Cannabis: Implications for Physical and Occupational Therapy

Editor's note: This text-based course is a transcript of the webinar, Cannabis: Implications for Physical and Occupational Therapy, presented by Melissa Bednarek, PT, DPT, PhD, CCS.

*Please also use the handout with this text course to supplement the material.

Learning Outcomes

• After this course, participants will be able to identify the various parts of the cannabis plant.
• After this course, participants will be able to describe routes of administration, the mechanism of action, and the side effects of cannabis.
• After this course, participants will be able to describe the implications of cannabis for physical and occupational therapy.

Introduction 

In terms of my approach to pharmacology, I have a background in physiology, and I find pharmacology less overwhelming when I can place it in the context of applied physiology. Throughout this course, I’ll review relevant physiology to help us understand how cannabis works within the body.

Cannabis is a very timely topic, and you likely have many questions. With that in mind, I will cover several different areas, giving you a bit of each. In preparing for this, I spoke with other therapists, colleagues, and friends and asked, “If you were going to listen to a course on cannabis, what would you want to know?” I used that feedback to shape this course.

We’ll touch on legal aspects, routes of administration, relevant physiology, purported benefits and risks, potential drug interactions, and conditions for which cannabis may be helpful. We’ll then consider the implications for PT and OT practice. As this is a pharmacology lecture, I’ll also review some basic pharmacology concepts, such as drug schedules and their meanings, as well as pharmacokinetics and pharmacodynamics, and then apply these principles specifically to cannabis.

The Cannabis Plant

Let us begin with the plant itself, because many of the confusing terms you hear come straight from it.

When we say cannabis in this context, we are usually referring to dried flowers, leaves, stems, and seeds of the Cannabis sativa plant. Culturally, you will hear it called marijuana, weed, pot, bud, and many other names. Those are all pointing back to plant material from Cannabis sativa.

Within that plant are more than 100 different cannabinoids. Two of them are most relevant to this discussion.

• Delta‑9‑tetrahydrocannabinol, or THC

  • This is the cannabinoid that produces the “high.”
  • When patients talk about feeling euphoric, relaxed, or “stoned,” that is THC at work on the endocannabinoid system.

• Cannabidiol, or CBD

  • CBD does not produce that same “high.”
  • It has physiologic effects, including on seizure activity and other systems, but is considered non‑intoxicating.

Only female cannabis plants produce flowers. Unfertilized female plants can have two to five times the concentration of cannabinoids such as THC compared with fertilized plants. The industry has taken full advantage of this, intentionally cultivating unfertilized female plants to produce high‑potency strains.

In terms of where cannabinoids are found in the plant, the greatest concentration is in the flowers, then the leaves, then the stems and stalks. Seeds do not contain cannabinoids. That matters when we later talk about hemp foods and about different forms of CBD.

Hemp

The term hemp adds another layer of confusion, and you will hear it constantly in regulations and marketing.

Hemp is defined as any part of the Cannabis sativa plant with no more than 0.3 percent THC by dry weight. That threshold is built into US federal law. Once THC goes above that cutoff, legally, we are no longer talking about hemp; we are talking about marijuana under federal law.

CBD can be derived from both hemp and non‑hemp cannabis. The 2018 US Department of Agriculture Farm Bill made CBD derived from hemp legal at the federal level, as long as the THC content remains at or below the 0.3 percent threshold. States can and do add their own restrictions, so federal legality does not automatically mean state legality.

You may also hear about delta‑8 and delta‑10 products. These are cannabinoids related to delta‑9‑THC:

• Delta‑9 is the form we usually mean when we say THC, and it is the most potent.
• Delta‑8 and delta‑10 occur naturally in tiny amounts in hemp, but most commercial products are made synthetically from hemp‑derived CBD.
• Potency appears to follow this pattern: delta-9> delta-8> delta-10.

Because these products are produced from federally legal hemp, manufacturers have used this as a loophole. However, delta‑8 and delta‑10 have been banned or heavily restricted in many states. So, again, legality depends significantly on where you and your patient are.

Forms of CBD

CBD shows up in a wide range of products, some therapeutic and some essentially lifestyle or wellness-oriented.

You may see CBD:

• In food
  • Cannabis seeds in baked goods, pizza crust, oils, beer, milk, chocolate, ice cream, and snack foods
  • Hemp seed flour as a gluten‑free alternative to wheat flour
• As oils 
• In lotions, balms, and creams
• In capsules and softgels
• In cosmetics and hair care products
• In dermatologic products, including items marketed for wound healing or inflammatory skin conditions

One crucial point is that hemp seeds and hemp seed flour themselves do not carry meaningful amounts of THC or CBD. Seeds do not contain cannabinoids; the cannabinoids reside in flowers and, to a lesser degree, leaves and stems. So if someone is using “hemp seed” foods, they are not getting physiologic doses of THC or CBD from the seeds alone.

History of Cannabis

Cannabis is not new. The plant has a long human history.

Use of extracts from Cannabis sativa can be traced back to China around 2900 BC. In the early 1800s, Western medicine began to explore cannabis more formally as a therapeutic agent.

CBD was first isolated in 1940, though its structure was not reported until 1963. Shortly thereafter, in 1964, the structure of THC was determined. As the scientific understanding of these cannabinoids grew, interest in the recreational use of cannabis increased significantly during the 1960s and 1970s."

Two milestones help explain why some of the newer research you see comes from outside the US.

• Canada officially legalized cannabis for recreational and medical use in 2018.
• Mexico legalized recreational use in 2021.

Once a country legalizes, it becomes easier to conduct prospective, randomized research with standardized products, which we will see in some of the studies referenced later.

Definition of Schedule Drugs

To understand where cannabis sits legally in the US, we have to touch on scheduled drugs.

In 1970, Congress passed the Comprehensive Drug Abuse Prevention and Control Act. A key part of this legislation is the Controlled Substances Act (CSA), which established the framework for regulating the manufacturing and dispensing of drugs. This system, which is enforced by the Drug Enforcement Administration (DEA), categorizes drugs into specific 'schedules' based on criteria like their potential for physical and psychological dependence.

• Schedule I

  • No currently accepted medical use
  • High potential for abuse
  • Examples: heroin, ecstasy (MDMA), LSD, and Marijuana (although some states have legalized marijuana if for medical and recreational use)

• Schedule II

  • High potential for abuse
  • Use may lead to severe psychological or physical dependence
  • Examples: hydromorphone or Dilaudid, Oxycodone or oxycontin, Fentanyl, and cocaine

• Schedule III

  • Moderate to low potential for physical and psychological dependence
  • Examples: Tylenol with codeine, anabolic steroids, ketamine, and suboxone

• Schedule IV

  • Low potential for abuse and low risk of dependence
  • Examples: Xanax, Darvocet, Valium, Ativan, Ambien, and Tramadol

• Schedule V

  • Lower potential for abuse than Schedule IV
  • Preparations contain limited quantities of certain narcotics
  • Often used as antidiarrheals, antitussives, or mild analgesics

This framework was established in the early 1970s and still drives how cannabis is handled at the federal level.

Legal Aspects – Federal

At the federal level, cannabis remains a Schedule I substance.

That classification means that, in the eyes of federal law, cannabis has high potential for dependency with no accepted medical use. This is true even though many states have broad medical and recreational markets and even though the FDA has approved some cannabis‑based or cannabis‑related medications, which we will discuss shortly.

Despite this schedule, cannabis is the most commonly used federally illegal drug in the United States. CDC data from 2022 suggests that about 61.9 million people used cannabis that year. Approximately three in ten people who use cannabis meet criteria for a cannabis use disorder.

This disconnect between federal classification and real‑world use is part of why clinicians feel pulled in multiple directions. Patients use it. States legalize it. The federal schedule says no medical use. That tension influences research, prescribing, and even education.

Legal Aspects-States

Now let us zoom in to the state level.

State laws vary significantly, and they are often subject to change. As of February 2024:

• Medical use

  • Forty‑seven states, the District of Columbia, and three US territories (Guam, Puerto Rico, and the US Virgin Islands) have legalized cannabis for medical use.
  • Idaho, Nebraska, and Kansas remain the states without legal medical cannabis programs. American Samoa is a US territory without legal medical cannabis.

• Non‑medical adult use (recreational use)

  • Twenty‑four states, the District of Columbia, and two territories (Guam and the Northern Mariana Islands) have legalized non‑medical adult use.

In some places, cannabis has been decriminalized rather than legalized. Decriminalization means that possession may still be technically illegal, but penalties shift from criminal to civil measures, such as fines. From a clinical standpoint, decriminalization can change patients' willingness to talk about their use.

The key message for you as a therapist is that your patients’ legal risk around cannabis can differ dramatically depending on where they live and work, even if their clinical presentation looks identical.

FDA Approved Versions

Even while whole‑plant cannabis remains Schedule I at the federal level, the FDA has approved specific cannabis‑related medications.

• Cannabidiol (Epidiolex)

  • A plant‑based drug that contains purified CBD.
  • Approved to treat seizures associated with certain rare forms of epilepsy.
  • This is not an over‑the‑counter CBD oil; it is a standardized pharmaceutical product.

• Dronabinol (Marinol, Syndros) and nabilone (Cesamet)

  • Synthetic drugs that mimic THC.
  • Approved to treat nausea and vomiting in people undergoing chemotherapy.
  • Also approved to stimulate appetite in people with AIDS.

So, at the same time that whole‑plant cannabis is labeled “no accepted medical use” at the Schedule I level, we have FDA‑approved formulations of cannabis‑related molecules. That inconsistency is part of the broader debate over rescheduling, which we will revisit later.

Back to Pharmacology

Since this is a pharmacology‑focused topic, I want to briefly frame cannabis in the same language we would use for any other drug class.

We will touch on pharmacokinetics, which refers to the body's actions on the drug, and pharmacodynamics, which refers to the drug's actions on the body. Then we will plug cannabis into that framework.

Pharmacokinetics

Pharmacokinetics looks at how the body absorbs, distributes, metabolizes, and eliminates a drug.

When we administer any drug, it is a foreign substance. The body responds by:

• Absorbing it into the bloodstream
• Distributing it to tissues
• Metabolizing it, mainly in the liver
• Excreting it, often via the kidneys and biliary system

Absorption is where routes of administration come in. For cannabis, the main routes your patients will use are:

• Oral(PO)

  • Per os (by mouth). The drug is ingested and passes through the gastrointestinal (GI) system.
  • Swallowed tablets, capsules, oils, or edibles.
  • Most common and convenient in general pharmacology.

  • Disadvantages:

    • Stomach Acidity: The low pH environment (designed to digest proteins) can inactivate certain drugs.

    • First-Pass Effect: Drugs absorbed from the GI tract go directly to the liver via the portal vein. The liver may break down the drug so quickly that it never reaches general circulation (e.g., Lidocaine).

    • Food Interactions: Certain foods or drinks can render drugs insoluble or cause adverse side effects.

• Sublingual

  • Drops or films placed under the tongue to dissolve.
  • Faster than oral because the drug is absorbed rapidly into the large blood vessels found under the mucous membranes of the mouth.
  • Advantage: It bypasses digestion and the liver, entering the bloodstream faster than oral administration (e.g., Nitroglycerin for chest pain). When a patient has chest pain, you want the drug in the system now to address it. 

• Topical

  • Applied to skin or mucous membranes (eyes, ears, nose, mouth)
  • Unlike other routes that aim for systemic distribution through the bloodstream, topicals generally act locally, although systemic absorption can occur depending on the formulation.

• Inhalation

  • Inhaling a gas, liquid, or powder (e.g., Albuterol for asthma).
  • The drug is absorbed directly into the bloodstream through the alveoli of the lungs.
  • Cannabis in gas, vapor, or fine particle form travels into the lungs and across the alveolar membrane into circulation.

Parenteral Administration (Routes outside the GI system)

• Subcutaneous: Injected into the fatty tissue under the skin (e.g., insulin). Absorption is slower because blood flow to fat is lower than it is to muscle.

• Intramuscular (IM): Injected into the muscle (e.g., vaccines). Absorption is faster due to a rich blood supply.

• Intravenous (IV): Injected directly into the bloodstream for immediate effect.

Bioavailability

Bioavailability is the proportion of a drug that actually enters circulation in active form. For cannabis, bioavailability varies by route and by compound.

For THC:

• Oral ingestion yields approximately 4 to 12 percent bioavailability.
• Inhalation can yield around 10-35 percent.

For CBD, oral bioavailability is reported to be around 6 percent, with inhaled forms reaching higher levels. These numbers are approximate and vary with the specific product and individual factors, but they give you a sense of why route matters so much when patients switch from smoking to edibles or vice versa.

After absorption, some cannabinoids bind to plasma proteins, such as albumin. While bound, a drug is essentially “offline.” As an unbound drug is taken up by tissues or metabolized, more drug is released from binding sites to keep an equilibrium. Only the unbound fraction can interact with receptors and exert pharmacologic effects.

Biotransformation

Definition: The process of transforming a drug from an active form to a less active or inactive form.

• Primary Site: The liver is the main location for breaking down drugs.

• The First-Pass Effect: Drugs entering via the GI tract travel through the portal vein to the liver before reaching the rest of the body.

• Clinical Considerations: Drug dosing must be adjusted for populations with compromised liver function, such as:

  • Older adults (age-related liver changes).

  • Premature infants.

  • Individuals with liver disease.

Excretion

Excretion of inactive metabolites occurs primarily via the kidneys into urine, and via bile into feces. Water-soluble drugs are easily excreted in urine. Fat-soluble drugs may need to be reabsorbed and processed by the liver multiple times until they become water-soluble enough for renal excretion. For orally administered cannabis, more than 65 percent may be excreted in feces and about 20 percent in urine.

All of this becomes crucial when we start thinking about drug interactions and about dosing intervals

Pharmacodynamics

While pharmacokinetics describes what the body does to a drug—encompassing absorption, distribution, metabolism, and excretion—pharmacodynamics focuses on the inverse: how the drug exerts its effect on the body. This process primarily takes place once the drug is unbound and capable of interacting at the receptor level. By engaging with these receptors, drugs initiate the biochemical changes that result in therapeutic outcomes.

At the molecular level, drugs generally function as either agonists or antagonists. An agonist is a substance that binds to a receptor and "unlocks" it, effectively triggering a specific physiologic action. A pertinent example of this mechanism is THC, which functions as an agonist at CB1 receptors. Conversely, an antagonist (or blocker) occupies the receptor site to prevent other ligands from activating it. A common clinical example is the administration of beta-blockers; these drugs lower heart rate by blocking beta-adrenergic receptors, thereby preventing stimulating substances like epinephrine and norepinephrine from binding and exerting their usual effects.

However, because no drug is perfectly selective, administration rarely results in only the intended therapeutic goal. It is important to distinguish between the different types of unintended outcomes. Side effects are drug effects other than the goal; they are generally expected and not surprising, even if they are unwanted. Adverse effects, by contrast, are severe, less common reactions that can be dangerous or life-threatening. For cannabis and related products, understanding the distinction between the primary therapeutic targets (cannabinoid receptors) and these potential unwanted clinical effects is essential for safe administration.

Routes of Administration

Common routes of administration for cannabis include:

• Smoked

  • Joints similar to cigarettes.
  • Blunts using cigar or cigar wrappers.
  • Bongs using glass or water pipes.

• Vaped

  • Vaporization of plant material or concentrates, often using vape pens.
  • Heats cannabis to release vapor but ideally avoids some of the combustion products of smoking.

• Mixed into food or drink

  • Edibles: baked goods, candies, beverages, oils, and more.

• Inhalation of oil concentrates or extracts

  • Often called “dabbing,” using highly concentrated THC or other cannabinoids.

From a clinical standpoint, different routes change:

• Onset time
• Peak effect
• Duration of action
• Likelihood of overdose or overconsumption
• Pulmonary versus GI impact

For example, smoked and vaped products have a rapid onset within minutes, which makes overconsumption less likely in a single sitting but raises respiratory concerns. Edibles have a delayed onset, often one to three hours, increasing overdose risk because people may redose before the first dose peaks.

Endocannabinoid System (ECS)

To fully understand the effects of cannabis, we must first examine the body’s own endocannabinoid system (ECS). The ECS is a naturally occurring neuromodulatory system found throughout the central and peripheral nervous systems, as well as in immune tissues. This system plays a critical regulatory role in maintaining homeostasis, controlling functions such as:

• Learning and memory: High doses of cannabis can cause temporary disruption of short-term memory due to ECS involvement in these pathways.

• Emotional processing and sleep.

• Physiologic regulation: Including temperature control, pain control, inflammatory responses, and immune function.

• Appetite and eating: The phenomenon colloquially known as "the munchies" is a direct result of cannabis activating ECS pathways that upregulate the desire for food.

System Components: Ligands and CB1 Receptors

The ECS is comprised of three main components: receptors, endogenous ligands (the body's own cannabinoids), and enzymes that synthesize and break down these ligands.

The primary receptor involved in the psychoactive effects of cannabis is the CB1 receptor. These are widely distributed in the brain but are also found in peripheral tissues, including adipocytes (fat cells), skeletal muscle, the exocrine pancreas, the liver, and the GI tract.

Cannabis Versus Opioids 

Cannabis and opioids are both controlled substances, but mechanistically, they are distinct.

• Cannabis interacts primarily with cannabinoid receptors (CB1 and CB2).
• Opioids interact with opioid receptors (mu, delta, and kappa).

Both systems naturally exist within the body. Just as we produce endocannabinoids, we also produce endogenous opioids like endorphins. Exogenous opioids like morphine or oxycodone, and exogenous cannabinoids like THC, plug into those respective systems.

The fact that these are two different receptor families helps explain why someone can be on both opioids and cannabis and experience complex interactions in pain modulation, mood, and cognition.

Mechanism of Action for Opioids

To distinguish cannabis from other analgesic classes, it is necessary to review the mechanism of action of opioids. Opioids act on a physiological system entirely separate from the endocannabinoid system (ECS). While the ECS utilizes CB1 and CB2 receptors, opioids operate by binding to specific opioid receptors in the central nervous system to block ascending pain impulses.

Opioids generally fall into three categories based on their origin:

• Naturally occurring endorphins: These are produced endogenously by the body. A common example of endogenous opioid release is the "runner's high" experienced after intense physical exertion.

• Plant-derived: Substances derived directly from the opium poppy (e.g., morphine).

• Synthetic: Manufactured molecules designed to mimic natural opioids at the receptor site.

Receptor Classification and Abuse Potential

The primary opioid receptors are distinct from cannabinoid receptors and are classified as:

• Mu (μ)
• Delta (δ)
• Kappa (κ)

The specific receptor to which a drug binds, and the strength of that activation, dictate both the drug's analgesic efficacy and its side effect profile. For instance, strong mu agonists (such as morphine) bind intensely to the Mu receptor. While this provides potent pain relief, it also creates a high potential for dependence and abuse.

In clinical practice, opioids are often combined with non-narcotic agents. The therapeutic rationale is that the non-narcotic (such as acetaminophen or aspirin) provides a foundation of pain relief, allowing for a lower dose of the opioid to be effective. This "layering" of mechanisms aims to minimize opioid side effects while managing pain. Common examples include:

• Percocet: A combination of acetaminophen and oxycodone.

• Lortab ASA: A combination of aspirin (acetylsalicylic acid) and hydrocodone.

It is vital to remember that cannabis is not simply a "different flavor" of opioid. It operates on a distinct biological system (the ECS). However, because both systems modulate pain and mood, their clinical uses often overlap, and they can interact within the patient.

Cannabis Versus Opioid Use

Current research suggests that cannabis use may reduce opioid use. I want to highlight a few specific studies to illustrate how researchers are examining this issue. Although this is not an exhaustive review, the recent articles provide valuable insights.

First, let's look at a 2021 prospective study published in the Journal of Pain Medicine titled, "Cannabis significantly reduces the use of prescription opioids and improves quality of life in authorized patients." This study took place in Canada, where cannabis was legalized in 2018, and involved a regulated, physician-supervised medical cannabis access program. Researchers looked at the impact of cannabis on prescription opioid use and quality of life over six months with a large sample size of 1,145 patients.

At baseline, 28% of participants were using opioids. By the end of the six months, that number dropped to 11%. Furthermore, the daily opioid use went from 152 morphine milligram equivalents (MME) at baseline down to 32.2 MME—a 78% reduction in mean opioid dosage. The answer to "Can cannabis help reduce opioid use?" appears to be yes. However, you will encounter discussions regarding whether we are simply swapping one drug for another. While cannabis is definitely an alternative amidst the opioid crisis, valid concerns regarding substitution remain.

Next, let's look at a study concerning cannabis and Opioid Use Disorder (OUD). This is a study by Lent and colleagues in the Journal of Cannabis Research titled, "Clinical and Psychosocial Changes in Adults with Opioid Use Disorder and Chronic Pain Using Medical Cannabis: A Brief Report." (Note: The full reference list accompanies this session).

This observational study was conducted in Philadelphia. Although medical cannabis is an approved treatment for OUD, little is known about its effects on illicit opioid use or the psychosocial factors preceding it. In this study, 47 adults with chronic pain who were taking buprenorphine or naloxone for OUD were enrolled. They were given funded access to THC: CBD capsules over three months. Researchers looked at outcomes including pain severity, self-efficacy, activity interference, and rates of illicit substance use (verified by urine drug screening).

They found that with access to the THC: CBD capsules, participants experienced a decrease in pain severity and pain interference. While there was no significant change in opioid use, they did report improvements in both sleep quality and quality of life.

Benefits of Cannabis

So, what are some of the benefits of cannabis? One of the challenges we face in discussing this is that it remains a Schedule I drug. As of today, it is still illegal at the federal level. Consequently, the ability to create high-quality research studies is limited.

The connection is that for any research involving human subjects, researchers must go through an Institutional Review Board (IRB) to ensure the safety of the subjects. Basically, no IRB is going to approve research—as well-designed as it may be—with a drug that the government has identified as having no medical use and a significant concern for dependence and addiction. Therein lies one of the challenges.

We have a whole "anecdotal world," but being able to design and conduct high-quality research is very challenging with cannabis because of that Schedule I classification. That is why, when I looked into the literature, it was interesting to see that much of the information comes from Canada and other countries where these legal barriers are different.

However, despite those challenges, let’s look at some of the purported benefits of cannabis.

Antimicrobial Effects

First, there are antimicrobial properties. Both THC and CBD are bacteriostatic and bactericidal against Gram-positive bacteria. So, when thinking about infection control, cannabis can be helpful.

Cancer and Symptom Management

Cannabinoids have been found to have anti-cancer properties, though the exact mechanism is unclear. Specifically, breast, lung, liver, and bladder cancers have been looked at in this regard.

Additionally, the anti-nausea and anti-vomiting effects of cannabis have been helpful for individuals with cancer, particularly regarding chemotherapy-related symptoms. As I mentioned earlier, there are FDA-approved medications available for this condition. Dronabinol and nabilone are synthetic drugs that mimic THC and are FDA-approved to treat nausea for individuals undergoing chemotherapy. These drugs are also indicated to increase appetite for individuals with AIDS.

Anti-Seizure

As discussed earlier, another FDA-approved drug is Epidiolex. This contains purified CBD (cannabidiol) and is approved to treat seizures associated with rare forms of epilepsy.

Neuroprotective Effects

Some studies have found a correlation between the endocannabinoid system and Parkinson's disease. The connection here is that the basal ganglia of the brain, which is involved in Parkinson's disease, is where many of the naturally occurring endocannabinoids are most concentrated.

Gastrointestinal Health

Ultimately, the endocannabinoid system (ECS) is present throughout the gut and regulates various digestive processes. Activating those ECS receptors can produce beneficial effects on GI motility, inflammation, and immune response. This suggests cannabis can produce beneficial effects on conditions such as Irritable Bowel Syndrome (IBS).

Adverse Effects of Cannabis

So, what are some of the adverse effects? Let's go through the concerns system by system.

Central Nervous System (CNS)

First, let's look at the central nervous system, distinguishing between short-term and long-term effects. In the short term—shortly after ingestion via whatever route of administration—there are concerns regarding impairments in cognition, memory, alertness, coordination, and balance.

From a therapy perspective, this is critical. Impairments in balance and coordination can increase the risk of falls, particularly in older adults or those with pre-existing neuromusculoskeletal conditions. Be aware that cannabis will impair the ability to think and react quickly; reaction times are decreased. This affects activities such as driving a car or other tasks that require concentration and alertness.

Long-term effects become more challenging to define. As I mentioned regarding legality, high-quality studies are limited in number. Therefore, much of our information on long-term effects comes primarily from individuals who have used cannabis recreationally over a long period. What we have seen is that long-term use can lead to decreased concentration and loss of interest in activities. It may also potentially increase symptoms of psychosis, depression, and other psychiatric disorders, especially in those who are susceptible.

A special note regarding children and adolescents: young people who ingest cannabis are especially susceptible to these mental health concerns. There are also significant concerns regarding the effects of cannabis on a developing central nervous system, which also applies to pregnancy.

Cardiovascular System

Moving on to the cardiovascular system, cannabis can have acute short-term effects, including tachycardia, increased blood pressure, and increased oxygen consumption by the heart. The prevailing thought is that this is mediated by the sympathetic nervous system.

Think about our role as therapists. One of our primary treatments is exercise, often in the form of aerobic exercise. If you are in a setting where you are asking patients to exercise, and they have recently used cannabis, they are starting at an elevated heart rate and blood pressure. Aerobic exercise will only elevate that further. These are real concerns from a therapy perspective.

There can also be an elevated risk of an acute myocardial infarction, likely due to coronary artery vasospasm, especially in the first hour after smoking cannabis. Because recreational use isn't medically supervised, individuals may not know if they are susceptible to this. Additionally, cannabis has been associated with an increased risk of acute ischemic stroke, particularly in younger individuals in their 20s, 30s, and 40s.

Pulmonary System

Pulmonary concerns primarily relate to the route of administration. If the individual is smoking cannabis, they are irritating the airways, which can decrease airflow. Long-term administration via smoking can cause airway inflammation, airway obstruction, and symptoms similar to excessive cigarette smoking, such as wheezing, coughing, and increased sputum production. Again, the route of administration significantly impacts this discussion.

Gastrointestinal System

Finally, looking at the GI system, cannabis can cause nausea and vomiting. This is somewhat paradoxical because, as I mentioned earlier, there are FDA-approved drugs (synthetic THC) used specifically to treat nausea and vomiting in individuals undergoing chemotherapy. It is a paradox that is difficult to explain: on one hand, it can cause these symptoms in some individuals, while in others, it is an effective treatment.

Risks of Cannabis

Moving briefly away from physiology, this is a good opportunity to mention the "gateway drug" theory. You will often hear concerns that an individual who starts utilizing cannabis may move on to more intense substances, such as heroin. While this is not a physiological effect, it is often cited as an adverse, unintended outcome.

Overconsumption

There are also specific risks associated with overconsumption, which is particularly true for edibles. When cannabis is taken orally, it must pass through the stomach and GI system, be absorbed, and then be broken down by the liver before entering the bloodstream. This process can take over an hour.

Consequently, individuals might think, "I didn't feel any effect," and consume more because they aren't allowing enough time for the drug to metabolize, compared to the rapid onset of smoking. This "stacking" of doses can lead to severe side effects.

Lack of Standard Dosing in Foods

Homemade edibles and even some commercial products can vary widely in dose per serving. Since there is no standard dosing within food products, this potential for overconsumption is high.

Appeal to Children

There is also the risk of appeal to children. As seen in the slides I shared earlier, Gummies, chocolates, and candies containing THC or CBD can easily be mistaken for regular treats, leading to unintentional pediatric exposures.

Contamination With Other Substances

There is the risk of contamination. With oral ingestion and food products, there is a risk of foodborne illnesses, such as Salmonella. Additionally, unregulated products may be contaminated with pesticides, heavy metals, solvents, or microbes, leading to foodborne illness or toxic exposures. 

Adverse Drug Interactions

These can involve both prescription drugs and over‑the‑counter or herbal products. This is a significant area of concern, particularly given polypharmacy in older adults.

Metabolism of Cannabis

All right, let's briefly go back into physiology. I want to give you the context regarding how cannabis is broken down.

The CYP Enzymes and Drug Metabolism

There is a family of enzymes in our body known as cytochrome enzymes (abbreviated CYP) that are responsible for drug metabolism, particularly in the liver. Within this family is a specific enzyme known as CYP3A4. This enzyme is responsible for breaking down THC.

Here is where it gets complicated: while CYP3A4 breaks down THC, cannabis can simultaneously inhibit the action of that enzyme.

If THC inhibits CYP3A4, the enzyme is no longer able to break down other drugs effectively it is responsible for metabolizing. Therefore, we have a significant potential for drug-drug interactions. If the enzyme is inhibited, the concentration of other drugs in the system increases because the usual metabolic pathway is blocked.

For example, if a patient takes a drug intended to lower blood pressure, but that drug isn't broken down because THC has inhibited the enzyme, the drug will continue to lower blood pressure beyond the intended point. The same applies to medications that lower blood glucose levels. If the drug isn't metabolized, the patient can end up with toxic levels.

Narrow Therapeutic Index

This is especially risky for drugs with a "narrow therapeutic index." This is a pharmacodynamic term meaning that the window between a therapeutic dose and a toxic dose is very narrow.

Warfarin (Coumadin).  Coumadin is a prime example. We know it has a narrow index because it requires frequent lab values (PT/INR) to monitor it. Compare this to aspirin, which has a wide therapeutic index and requires no monitoring. If a patient is on a drug with a narrow index like Warfarin, and cannabis inhibits its breakdown, they can quickly spill over into toxic levels despite taking their usual dose.

Interactions with Prescription Drugs

Let’s look at specific prescription drugs metabolized by CYP3A4 that can interact with cannabis:

• Calcium Channel Blockers: (e.g., Amlodipine, Nifedipine). If a patient is taking these for blood pressure, cannabis limits the body's ability to break them down. When the next dose comes along, the drug levels stack, and the patient's blood pressure could bottom out.

• Macrolide Antibiotics: (e.g., Erythromycin).

• Benzodiazepines: (e.g., Alprazolam, Lorazepam). If not broken down, their sedative effects are prolonged.

• Statins: (e.g., Atorvastatin, Rosuvastatin).

• HIV Medications: Specifically, the protease inhibitors.

• Corticosteroids.

• Warfarin (Coumadin): THC inhibits the breakdown of this drug, leading to an elevated INR and an increased risk of bleeding.

These are common medications. Many of your patients will be on one or more of these. If they are utilizing cannabis, especially if they are not reporting it, these are valid clinical concerns.

Interactions With Over-The-Counter (OTC) Drugs

It is not just prescription drugs; we must also consider OTC medications and supplements:

• NSAIDs: Using cannabis with non-steroidal anti-inflammatories can result in an increased risk of GI bleeds.

• Antihistamines: Can result in increased drowsiness.

• Melatonin and Valerian Root: Can interact with cannabis to further impair cognitive and motor function.

• Echinacea: This supplement can inhibit the enzymes that normally break down THC, leading to higher levels of THC in the system and increased effects.

• St. John’s Wort: This functions differently. It can actually induce the enzyme to work faster, resulting in a reduction of the effects of THC. Consequently, an individual taking St. John's Wort might take higher doses of cannabis to achieve the desired effect, leading to other complications.

This serves as a reminder: Are we asking our patients about OTC drugs, NSAIDs, herbal supplements, and vitamins? Patients often do not think these substances are relevant to report, just as they are unlikely to report their cannabis use.

Effects of Cannabis Depend On..

Finally, the severity of these effects depends on several variables:

1. Concentration and Frequency: How potent is the THC, and is it used daily or recreationally?

2. Polysubstance Use: Are they using alcohol or other substances?

3. Route of Administration: As I mentioned earlier, oral ingestion (edibles) is absorbed more slowly and is less consistent due to stomach contents. Because edibles take 1 to 3 hours to reach peak levels and must pass through the liver, they have a higher likelihood of interacting with other medications compared to inhalation.

Additionally, because of the delayed onset with edibles, there is a risk that an individual will not feel the effects immediately and will "overdose" by taking additional doses. When you combine this with individual traits such as sex, genetics, and physiology, predicting these effects becomes very challenging without large-scale, randomized controlled trials.

Side Effects of CBD

There is limited FDA data on safety due to the legal perspectives we have discussed, but we do know that CBD, in particular, can lead to liver damage. Considering how much I have emphasized the liver's role in drug metabolism, hopefully, this does not come as a surprise.

Other common side effects include:

• Drowsiness

• Diarrhea

• Changes in appetite

• Changes in mood

• Interactions with other drugs (as previously detailed)

Additionally, the CDC specifically states that CBD is not recommended during pregnancy or while breastfeeding. This aligns with the concerns I mentioned earlier regarding the potential effects of cannabis on a developing central nervous system.

Cannabis and Spasticity

We are going to move on to discuss specific medical conditions. This is not meant to be an exhaustive list, but rather a highlight of conditions you may have experienced with your patients or perhaps have wondered about. I want to review a specific study to illustrate how researchers are currently viewing these applications.

The first condition we will discuss is spasticity. There is a relevant 2012 study published in the Canadian Medical Association Journal entitled, "Smoked Cannabis for Spasticity and Multiple Sclerosis: A Randomized Placebo-Controlled Trial."

Interestingly, even though it was published in a Canadian journal, the study actually took place in the United States. Canada often has more leeway for randomized placebo-controlled trials, but in this instance, the U.S. was the setting.

Methodology

The researchers investigated the short-term effects of smoked cannabis—specifically containing THC—on spasticity in individuals with Multiple Sclerosis (MS). Ultimately, 30 participants completed the study. The protocol involved smoking cannabis (with THC) or placebo cigarettes once daily for three days.

To be eligible, individuals had to have spasticity defined as at least a moderate increase in tone. This was quantified as a score of greater than or equal to 3 points on the Modified Ashworth Scale (MAS) at the elbow, hip, or knee.

The Modified Ashworth Scale. Just as a reminder, here is the breakdown of the scale used:

• 0: No increase in muscle tone.

• 1: Slight increase manifested by a catch and release with minimal resistance.

• 2: Slight increase with a catch followed by minimal resistance through a portion of the range.

• 3: Marked resistance, but the body part can still be moved.

• 4: Considerable increase in tone with difficult passive movement.

• 5: Affected parts are rigid in flexion and extension.

Results

The researchers combined ratings for the elbows, hips, and knees for a total possible score of 30. The mean baseline score among participants was 9 out of 30. The researchers determined ahead of time that a difference of 2 or more points would be considered clinically meaningful.

So, what did they find? They found an average reduction of 2.74 points. Given the baseline of 9, a drop of 2.74 points is a clinically meaningful improvement in spasticity.

Secondary Outcomes

• Pain: They utilized a Visual Analog Scale (0–100) and found pain was significantly reduced by an average of 5.28 points.

• Functional Mobility: They looked at timed walks and found no change.

• Adverse Effects: Participants did report some acute cognitive effects, which, given that the cannabis contained THC, is not surprising.

It is important to remember that these results were observed over a short duration of just three days. Regarding the exact mechanism of how cannabis reduces spasticity, the study did not define it, and we are not yet entirely sure how it works within the endocannabinoid system.

Cannabis and Musculoskeletal (MSK) Pain

Another condition frequently discussed in the context of cannabis is musculoskeletal pain.

A 2024 study in the Journal of Cannabis Research titled "Understanding the Epidemiology and Perceived Efficacy of Cannabis Use in Patients with Chronic Musculoskeletal Pain" took place in Canada at an orthopedic clinic and involved 629 patients with chronic musculoskeletal pain.

Why is this patient population of interest? These individuals are often drawn to cannabis because of its purported analgesic and anti-inflammatory properties.

Usage and Efficacy

Upon investigation, the researchers found that of the 629 individuals, 23%—almost a quarter—reported either past or present use of cannabis for their musculoskeletal pain. Of those users, the majority (63.7%) reported that it was either "very" or "somewhat" effective for their pain.

When analyzing the demographics to determine who was utilizing cannabis, the strongest predictor was a history of recreational cannabis use.

Barriers for Non-Users

This leaves us with three out of four patients who did not report use. Among these non-users, an overwhelming majority (63.7%) expressed interest in the option of cannabis for their musculoskeletal pain. However, when asked why they had not used it, they cited several specific barriers:

1. Lack of Knowledge: Specifically regarding different formulations and routes of administration. This confirms why this topic can get so confusing for patients.

2. Access: Uncertainty on how to obtain it. Although there are state laws, the federal illegality complicates patients' understanding of access.

3. Side Effects: A lack of awareness regarding potential side effects or general fear of them.

4. Stigma: The social stigma that remains associated with cannabis use.

This study highlights that while interest is high, significant educational and social barriers prevent patients from exploring this treatment option.

CBD and Mental Health

In 2020, a systematic review titled The Therapeutic Role of Cannabidiol in Mental Health: A Systematic Review was published. This review assessed the evidence and assigned recommendation grades (A, B, C, and D).

I have summarized the key findings below. While I won't go through every detail here, the full study is available in the reference list for your review if you are interested in the specifics.

Moderate Recommendations

Based on the literature, the researchers found a moderate recommendation for the use of CBD (specifically CBD, not THC) in the treatment of:

• Schizophrenia

• Social Anxiety Disorder

• Autism Spectrum Disorder (ASD)

• Attention Deficit Hyperactivity Disorder (ADHD)

Weak Recommendations

They found a weak recommendation for the use of CBD in the treatment of:

• Insomnia

• General Anxiety

• Bipolar Disorder

• Post-Traumatic Stress Disorder (PTSD)

• Tourette Syndrome

As I mentioned, these references are quite recent, so we expect to see more data emerge as time goes on. However, I wanted to highlight these three specific areas—spasticity, musculoskeletal pain, and mental health—to show you where the current literature stands regarding cannabis use.

Special Populations: Athletes

Some of you may be interested in the impact on athletes, as people are increasingly using cannabis in conjunction with exercise for a wide variety of perceived benefits. Some reports indicate that smoking is the most common route of administration for this population, often used to enhance performance, aid in recovery, or simply for recreational purposes.

Let's look at a 2024 study published in the Journal of Applied Physiology (American Physiological Society). This study was part of a larger registered clinical trial approved by Health Canada and an Institutional Review Board (IRB).

Methodology

This was a semi-randomized crossover study involving 14 participants with an average age of 23. They were recruited from the community and local club-level cycling and rowing teams. The researchers examined the exercise response after cannabis inhalation under four conditions:

1. Smoking THC-predominant cannabis.

2. Vaporizing THC-predominant cannabis.

3. Inhaling aerosol CBD-predominant cannabis.

4. A control group.

The study measured exercise capacity using cycling at submaximal levels followed by a maximal 20-minute time trial.

Key Findings

The results showed that heart rate was higher during submaximal exercise with the THC-predominant cannabis compared to CBD or the control. Furthermore, during the maximal 20-minute time trial, the power output was significantly lower with THC-predominant cannabis.

Some key takeaways include:

• THC Impairs Performance: Cannabis containing THC altered the physiological response to both maximal and submaximal exercise. It negatively impacted vigorous exercise performance as evidenced by the lower power output in the time trial.

• Method Didn't Matter: The negative effects occurred whether the THC was smoked or vaporized. The presence of THC was the key variable, not the method of inhalation.

• CBD Had No Effect: The CBD-predominant condition showed no significant effect on exercise response or performance compared to the control.

Route of Administration and Physiology

The authors noted that other studies looking at maximal exercise with edibles found no effect on performance. This provides further evidence that the route of administration (inhalation) plays a significant role in the cardiorespiratory effects on exercise capacity.

Psychological Impacts

Interestingly, despite the lower power output in the THC group, there was no difference in the Rate of Perceived Exertion (RPE). The participants performed worse physically, but reported the same level of exertion.

Anecdotally, participants believed their performance would be improved during the THC sessions. This is likely due to the effects of THC on pain and anxiety, creating an expectation of better performance. However, the data showed that—at least via inhalation—performance was actually impaired.

Implications for Therapy 

We will conclude this course by examining the implications for therapy, specifically, applying this to our roles as Physical Therapists (PTs) and Occupational Therapists (OTs). While I have references for both PT and OT literature, the underlying message and implications remain the same across both disciplines.

Patients and caregivers are often interested in alternatives to traditional therapy to decrease pain, inflammation, or spasticity, and they will naturally ask us questions. Because of this, we must possess the necessary knowledge regarding our role in medication management. For example, my background is in acute care, but I have also worked extensively in home health. In the home health setting, where medication reconciliation is a standard process, it is a natural connection for patients to ask us questions related to cannabis.

So, what exactly is the role of physical or occupational therapy?

The Bottom Line: Education, Not Advice.

I have reviewed the literature, and currently, there are no official statements from the APTA (American Physical Therapy Association) or AOTA (American Occupational Therapy Association) on this specific topic. However, the message they send is clear: We, as therapists, can provide education, but not advice.

Think about everything we have discussed over the last hour and a half. All of that is appropriate information to share with patients:

• The legal status of cannabis.

• Routes of administration.

• How it acts within the body’s systems.

• Potential benefits, concerns, risks, and drug interactions.

Providing that factual education is within our scope. However, we are not providing advice. If a patient asks, "I’m thinking about using cannabis for my chronic pain; do you think I should take it?" we should not answer with a definitive "Yes, do it." Instead, we provide the educational context and then refer them back to their physician.

Our role includes collaborating with other healthcare providers to ensure we are acting in the best interest of the patient. It is also our responsibility to stay informed. As I mentioned earlier, this information changes frequently. Many of the references I provided are very recent, precisely because laws and research are constantly evolving.

Ultimately, this approach is not really different from how we handle any other drug. If a patient asks, "Should I start taking a beta blocker?" we would respond by explaining what a beta blocker is, its function, and its potential benefits, risks, and interactions. We would then conclude by saying, "But you need to talk to your physician."

Cannabis recommendations should be treated with the same professional standard as any other pharmaceutical intervention related to physical and occupational therapy.

Implications for Physical Therapy

Looking specifically at the physical therapy literature, we need to shift modes if a patient is already using cannabis. In this scenario, our primary responsibility is to monitor for adverse effects. Again, this is no different from any other drug; if a patient is on a beta-blocker, we still monitor for adverse effects.

However, there are specific factors that are relevant to monitoring cannabis use:

Periodic Assessment of Pain

If a patient is using cannabis for chronic pain, we need to determine if it is actually decreasing their pain levels. We have methods and objective measures for evaluating pain, so we must ask: Are we measuring it effectively? Is the cannabis truly providing a benefit, or is it having no effect?

Fall Risk

We must examine our outcome measures to determine if the patient is demonstrating an increased risk or concern for falls.

Based on these assessments, are there recommendations we can make? For example, would we recommend the use of an assistive device? We need to think about what is within our specific toolbox as therapists to mitigate these risks.

Mood and Cognition

One of the unique aspects of our profession is that we spend a significant amount of time with our patients, often more than other healthcare providers. This allows us to really get to know them. Because of this, we are well-positioned to notice changes in mood and cognition, which can be side effects of long-term use. If we observe these changes, we must ensure that the patient is referred to the appropriate provider as needed.

Excessive Use and Drug Interactions

Finally, we must monitor for any excessive or untoward use, especially in conjunction with alcohol or opioids. While I previously discussed how cannabis can be used to reduce opioid consumption, that process must happen in a coordinated, medically supervised way. If we notice signs of mixing substances or uncoordinated use, we must refer the patient to a specialist immediately.

Implications for Occupational Therapy 

Turning now to occupational therapy. I admit, my background is in physical therapy, but through working with my OT colleagues and reviewing the literature, I have learned a great deal about their distinct perspective. One of the central tenets of the profession is the belief that humans are occupational beings and that engagement in occupation promotes health, well-being, and survival.

The Concept of "Non-Sanctioned" Occupations

However, recent discussions in the literature have added nuance to this idea. While occupation is generally positive, researchers are now asking: What about non-sanctioned occupations? This term refers to activities that might be unhealthy, socially unacceptable, or morally complex. This is where drug use enters the conversation.

Findings from the Literature (Guyonet, 2023)

In particular, a 2023 scoping review by Guyonet examined 14 studies that looked at cannabis use specifically as an occupation. This review highlights a shift in the framework, acknowledging these behaviors without judgment to understand the patient's reality.

The review identified several reasons why individuals view cannabis as an integral part of their occupation:

• Preservation of Life: Participants reported that cannabis helped them function, work, socialize, and control how the world perceived them.

• Endurance: It helped them endure the sometimes monotonous or mundane routine of everyday life.

• Enhancement: Some individuals used it to increase creativity or spirituality.

Essentially, these individuals viewed this "non-sanctioned occupation" as a tool to achieve the traditional OT goals of health, well-being, and survival.

While there is specific literature distinguishing PT and OT perspectives, the bottom line for both professions remains the same. As therapists, we are here to provide education on cannabis and to monitor our patients diligently for side effects.

Case Study-Mr. D

I use these hypothetical case studies to intertwine the pharmacology information we have discussed into a practical patient scenario. Currently, that information is likely stored in separate mental compartments, so let’s bring it together.

Patient Profile

Meet Mr. D. He is a 62-year-old male with a history of osteoarthritis and chronic pain who recently underwent a right total knee replacement. You are treating him in Pennsylvania, and he reports using edibles to manage his chronic pain.

Clinical Considerations

Beyond standard post-operative care for his knee, there are several specific factors to consider regarding his cannabis use:

1. Medical History and Opioid Use. First, we need to investigate his history of pain management. Has he taken opioids in the past? Is he currently taking them? As I mentioned earlier, there is evidence suggesting cannabis can help reduce opioid consumption, but we need to understand his specific baseline to treat him effectively.

2. Legal Context. Since this scenario takes place in Pennsylvania, it is essential to note that cannabis is legal for medical use in this state.

3. Route of Administration:. He reports taking edibles, which involve oral ingestion. The substance must be digested in the stomach and processed by the liver before entering the bloodstream. Due to this "first-pass" metabolism, the onset of effects can occur anywhere from one to three hours. This delay creates a risk of overconsumption. Is he looking for a faster effect? If he doesn't feel relief immediately, he might take more than needed before the first dose kicks in.

4. Monitoring Effectiveness and Safety, Since Mr. D is already using cannabis, our role shifts from education to monitoring.

• Pain Assessment: Is the cannabis actually reducing his pain? We need to use objective measures to verify this, especially with the added complexity of surgical pain.
• Fall Risk: He is already recovering from a total knee replacement, so he is likely using an assistive device. Does the cannabis introduce additional dizziness or balance issues that increase his fall risk?
• Mood and Cognition: Are there observable changes in his mental status?

5. Physiological Responses to Exercise. Finally, consider the implications for his rehab exercises. Total knee replacement therapy involves improving range of motion, strengthening, and often aerobic work.

We know that cannabis use can cause an increase in heart rate and blood pressure. If Mr. D takes his edible prior to your session for pain control, he may be starting therapy with elevated vitals before he even begins to exercise. This is a critical physiological factor to monitor during his session.

Case Study-Mrs. G

Let’s examine a different scenario.

Patient Profile

Our patient is a 44-year-old female diagnosed with HER2-negative breast cancer. She is currently undergoing a chemotherapy regimen that includes docetaxel, doxorubicin, and cyclophosphamide. She lives in California and reports smoking cannabis to manage her nausea and vomiting.

Clinical Context

Just as a side note, HER2-negative breast cancer is a type where the cancer cells do not express the HER2 protein on their surface. This accounts for about 70% to 80% of breast cancer cases, and the primary treatment is chemotherapy. To understand her situation, we need to look at why chemotherapy causes side effects like hair loss, nausea, and vomiting.

At a high level, cancer cells are abnormal because they undergo rapid cell division. Chemotherapy drugs differ in their specific mechanisms, but they generally work by targeting and destroying rapidly dividing cells.

However, cancer cells are not the only rapidly dividing cells in the body. We also have rapidly dividing cells in our hair follicles and in the epithelium (lining) of the GI tract. Because chemotherapy drugs are often not specific enough to target only the cancer, they inadvertently attack these healthy cells as well. This damage to the hair follicles causes hair loss, and the damage to the GI lining causes nausea and vomiting.

Analyzing the Cannabis Use

This patient is smoking cannabis specifically to treat that nausea. There are several factors we need to weigh here:

• Route of Administration (Smoking): Smoking offers quicker absorption compared to edibles. This means the patient gets immediate relief, which is often necessary when dealing with acute nausea. It also carries less risk of overconsumption compared to edibles, where the delayed onset can lead patients to take too much.

• Pulmonary Risks: Although absorption is faster, we must consider the potential pulmonary effects of inhaling smoke, as discussed earlier.

• The "Nausea Paradox": We must keep in mind the paradoxical effect of cannabis. While it is often used to treat nausea, in some cases (such as Cannabinoid Hyperemesis Syndrome), it can actually cause nausea and vomiting. We need to determine if it is truly helpful for her, or potentially complicating her symptoms.

Finally, it is worth remembering that there are FDA-approved synthetic cannabinoids specifically indicated for the treatment of nausea and vomiting associated with chemotherapy. This is a regulated option that avoids the pulmonary risks of smoking.

Case Study-Mrs T 

Patient Profile

Mrs. T is a 26-year-old female with Relapsing-Remitting Multiple Sclerosis (RRMS). She specifically asks you about the use of cannabis to address the significant spasticity she is experiencing.

Clinical Context: To provide some context, Relapsing-Remitting MS is the most common type of the disease. It is characterized by specific patterns:

• Relapsing: Periods of new or worsening symptoms.

• Remitting: Periods of partial or complete recovery.

Mrs. T is currently navigating this condition and looking for treatment options for her spasticity.

Therapist's Role

This brings us back to our defined role: providing education and then referring the patient to a physician. But even knowing where to start can be a challenge. Before this session, would you have felt comfortable looking into the evidence regarding cannabis use for spasticity and associated pain?

As I shared earlier, there is factual evidence that cannabis can be beneficial in reducing spasticity and pain. That is a fact. We can provide the patient with those references. However, we are not saying, "Yes, you should do that," or "You should think about doing this." We provide the information and then refer them back to their provider for further discussion.

Scope of Practice and Drug Interactions

Hopefully, the details I provided earlier regarding drug interactions highlight why this referral is so critical. Managing these interactions is way beyond our scope as therapists. We do not prescribe. Even if we have access to the patient's full medication list, trying to determine how cannabis might interact with their current regimen gets complicated very quickly. That analysis belongs with the physician or pharmacist.

Rescheduling of Cannabis

I want to add some additional context here. Throughout the last hour and 45 minutes, you may have found yourself thinking, "Wait a minute, she keeps saying it is Schedule I and illegal at the federal level. But didn't I see a news clip about rescheduling? What is the story there?"

Basically, the world currently exists with cannabis as a Schedule I drug. However, here is the update on the situation as of this month, September 2025.

The Review Process (2022–2023)

Back in October 2022, President Biden asked the U.S. Department of Health and Human Services (HHS) and the DEA to review how marijuana was scheduled under the Controlled Substances Act.

Before the DEA can propose rescheduling a substance, the HHS must provide a scientific and medical evaluation and a recommendation. They completed this review and, in August 2023, recommended to the DEA that cannabis be moved from Schedule I to Schedule III.

This was a significant moment. By suggesting Schedule III, it was the first time in more than 50 years that the government acknowledged cannabis has accepted medical uses—a key distinction from the definition of a Schedule I drug.

The Proposal and Current Delays (2024–2025)

Following that recommendation, the DEA proposed a rule in May 2024 to transfer marijuana to Schedule III. This initiated a public comment period, which received roughly 42,000 comments.

A hearing was scheduled for January of this year (2025), but an indefinite stay was placed on the proceedings to work through various legal hurdles. Consequently, as of this month, September 2025, the Trump administration is still reviewing the proposal. So, while you likely remember hearing about potential changes, as of today, it remains a Schedule I drug.

Implications of Rescheduling

If the status were to change, what would the impact be?

• Legal Consequences: It would no longer be an illegal drug at the federal level.

• Research: It would significantly open up research opportunities. We could move beyond anecdotal reports and conduct large, randomized controlled trials under controlled conditions to establish a stronger evidentiary basis.

• Drug Development: It would facilitate the development of new cannabis-based medications.

It would be a massive shift in the landscape, but for now, we remain in a holding pattern.

Summary

Cannabis is confusing. The legal aspects are confusing. The medical and pharmacologic aspects are confusing. And yet your patients are using it, your colleagues are talking about it, and your practice is affected whether or not cannabis is prescribed by someone on the team.

As therapists, it is our responsibility to remain up to date. That does not mean you need to be a cannabis specialist, but it does mean:

• You understand the basic plant, the key cannabinoids, and common routes of administration.
• You can describe benefits and risks in language that patients can understand.
• You recognize drug interaction concerns and know when to refer.
• You view cannabis use in the context of function, participation, and safety.

The role of physical and occupational therapy may include:

• Patient education on cannabis. That education is similar to the education you would provide about beta blockers or opioids.
• Monitoring for effectiveness in addressing symptoms such as pain, spasticity, or nausea, through functional outcomes, not just self‑report.
• Monitoring for side effects related to balance, cognition, cardiovascular responses, and mood.
• Referral to physicians or other prescribers when you see concerning patterns or when patients are seeking specific dosing or prescribing guidance.

If you keep that framework in mind, education, observation, and referral, you can support your patients in making more informed choices about cannabis, while staying well within your professional scope.

Questions and Answers

What is cannabis use disorder?

Cannabis use disorder is the term used to describe a pattern of cannabis use that becomes problematic. It is similar in concept to opioid use disorder. People with a cannabis use disorder continue using despite negative consequences, may have trouble cutting down, may use more than intended, and may experience withdrawal‑type symptoms or cravings when they try to stop.

Epidemiologic data suggest that roughly three in ten people who use cannabis meet criteria for a cannabis use disorder.

Is a narrow therapeutic index the same thing as a drug’s half‑life?

No. These are two different concepts.

• Narrow therapeutic index

  • This refers to how small the window is between a drug’s therapeutic level and its toxic level.
  • If that window is narrow, it does not take much of a dose change or interaction to push a patient from “therapeutic” to “toxic.”
  • Warfarin (Coumadin) is a classic example. We monitor it closely with lab values, such as INR, to ensure it stays within that narrow window.

• Half‑life

  • This is the amount of time it takes for the concentration of a drug in the body to fall by half.
  • Some drugs have short half‑lives and are cleared quickly; others have long half‑lives and linger for many hours or days.
  • For example, if a drug has a 30‑hour half‑life, and a person takes 10 mg at 8 a.m. on Monday, about 5 mg would remain around 2 p.m. on Tuesday, and roughly 2.5 mg would still be present about 30 hours after that.

A drug can have a narrow therapeutic index, a long half‑life, or both. When a drug has both a narrow therapeutic index and a long half‑life, dosing and interactions become especially critical. That is where adding cannabis and its enzyme effects can create problems if metabolism is inhibited and levels climb unexpectedly.

How close are we to being able to tell when someone last used THC on an employment drug test?

Standard employment drug tests can usually tell if THC metabolites are present, but not precisely when the person last used cannabis. Detection windows depend on:

• The test type (urine, blood, hair, etc.)
• The frequency of use (occasional versus daily)
• The person’s metabolism and body composition
• The sensitivity of the assay

An additional wrinkle is the rise of delta‑8 and delta‑10 products derived from hemp. Even though these use a “hemp” source, they can still lead to a positive THC‑related result on many tests. So while tests can say “THC or a related metabolite is present,” they are not very good at telling you whether use was last night or last week.

In the Corey‑Bloom MS spasticity study, could the reduction in spasticity just be from pain relief?

That is a fair question. Pain and spasticity can influence each other, and reducing pain can sometimes lead to what appears to be a reduction in tone.

The Corey‑Bloom study measured both spasticity (using the Modified Ashworth Scale) and pain (using a visual analog scale), and both improved over the three days with smoked cannabis versus placebo. The study did not fully disentangle the extent to which the spasticity change was independent of pain relief.

At this point, we can say that smoked cannabis in that trial produced clinically meaningful reductions in both pain and spasticity in the short term. Still, we cannot definitively say that spasticity reduction was entirely independent of improved pain. This is an area where further research would be beneficial, particularly through larger and longer-term studies.

References

Please refer to the additional handout.