How Cannabis Impacts Health & the Potential Risks | Dr. Matthew Hill
Dr. Matthew Hill, a professor at the University of Calgary, discusses cannabis biology, including THC vs. CBD effects, routes of administration, and the link between cannabis use and mental health conditions like psychosis and anxiety. He clarifies common misconceptions and potential benefits and risks.
Deep Dive Analysis
27 Topic Outline
Introduction to Cannabis, THC, CBD, and Terpenes
Describing the Psychoactive Effects and Cannabis 'High'
Cannabis and Brain Function: CB1 Receptor and Endocannabinoids
Types of Endocannabinoids: Anandamide and 2-AG
The 'Munchies': Cannabis and Appetite Stimulation
THC Pharmacology and Comparison to Anandamide
THC, CB1 Receptors, and Intoxication Mechanisms
Cannabis Effects on Focus and Memory
Routes of Cannabis Administration and Concentration
Self-Regulation of THC Intake and Concentrates
Addiction and Cannabis Use Disorder
Cannabis Legalization, Use Trends, and Edible-Related ER Visits
Oral Consumption of Edibles: Dosing and Time Course
Cannabis and Drug Testing: Detection and Influencing Factors
Cannabis and Hormones: Testosterone, Estrogen, and Sperm Quality
Cannabis Use During Pregnancy
Vaping Cannabis Products
Cannabis, Psychosis, and Anxiety
Cannabis, Psychosis, Schizophrenia, and Genetics
Cannabis Use and Schizophrenia: Causality vs. Predisposition
Cannabis Strains: Indica, Sativa, and Expectancy Bias
CBD: Pediatric Epilepsy, Adenosine, and Efficacy
Entourage Effect, Placebo Effect, and CBD Doses
Cannabis Health Risks: Cardiovascular and Other Concerns
Cannabinoid Hyperemesis Syndrome (Cyclic Vomiting Syndrome)
Potential Cannabis Benefits: Pain, Stress, Anxiety, and PTSD
Cannabis and Anxiety: Anandamide and Stress Response
9 Key Concepts
Cannabinoid Type 1 (CB1) Receptor
The most widely expressed receptor in the brain, primarily mediating the psychoactive effects of THC. Its physiological role is to maintain homeostasis by regulating neurotransmitter release, acting as a circuit breaker to prevent runaway excitation or inhibition of neurons.
Endocannabinoids
Molecules naturally produced by the body, such as anandamide and 2-AG, that bind to cannabinoid receptors. They are unique in that they are released from the postsynaptic neuron and travel backward to the presynaptic neuron to regulate neurotransmitter release, thereby maintaining neural homeostasis.
Retrograde Signaling
A distinct form of neurotransmission where endocannabinoids are produced by the postsynaptic neuron and then travel backward across the synapse to act on the presynaptic neuron. This mechanism allows for fine-tuned regulation of how much neurotransmitter is released by the presynaptic cell.
Anandamide
One of the two primary endocannabinoids, named from the Sanskrit word for bliss. It is characterized as a high-affinity, low-efficacy molecule that may play a tonic role in setting the steady state of brain circuits, contributing to baseline neural regulation.
2-Arachidonylglycerol (2-AG)
The second primary endocannabinoid, which has lower affinity but higher efficacy at the CB1 receptor compared to anandamide. It is thought to act in a phasic, on-demand manner, being rapidly produced during significant neural activity to powerfully adjust circuit function.
Cannabis Use Disorder
A problematic pattern of cannabis use leading to clinically significant impairment or distress, with diagnostic criteria similar to other substance use disorders. It can manifest as preoccupation with cannabis, failure to meet responsibilities, and withdrawal symptoms upon cessation.
Expectancy Bias
A psychological phenomenon where an individual's expectations about a substance's effects significantly influence their subjective experience. In cannabis use, what a person is told about a particular strain (e.g., 'sativa for energy') often strongly predicts the effects they report feeling.
Entourage Effect
A theoretical concept suggesting that the various compounds in the cannabis plant (THC, CBD, terpenes, minor cannabinoids) interact synergistically. This interaction is hypothesized to produce a combined effect that is different from, or greater than, the sum of their individual effects when isolated.
Cannabinoid Hyperemesis Syndrome (Cyclic Vomiting Syndrome)
A rare but real condition observed in some heavy, chronic cannabis users, characterized by intractable, recurring episodes of severe nausea and vomiting. Bizarrely, a hot shower or capsaicin cream has been reported to alleviate its symptoms, suggesting a link to thermoregulation or autonomic balance.
12 Questions Answered
The primary psychoactive component is delta-9 tetrahydrocannabinol (THC), which dictates the intoxicating and psychoactive properties. Cannabidiol (CBD) is another prominent cannabinoid, but it is not intoxicating.
THC primarily acts on cannabinoid type 1 (CB1) receptors, which are widely expressed throughout the brain. Unlike the body's own endocannabinoids that act in a targeted way, ingested THC indiscriminately activates these receptors across many brain networks, altering information processing and perception.
THC activates CB1 receptors in feeding circuits in the hypothalamus and reward circuitry, mimicking the brain's response to fasting. This enhances the reward value of food and overrides satiety signals, leading to increased food-seeking and consumption, particularly of high-calorie foods.
Yes, people can develop cannabis use disorder, which is defined by criteria similar to other substance use disorders, involving preoccupation with the drug, inability to meet responsibilities, and withdrawal symptoms if use is stopped. For weekly users, the propensity for developing a use disorder is around 30%.
Inhaling cannabis (smoking/vaping plant matter) leads to rapid onset (2-5 minutes) and shorter duration (2-4 hours) of effects due to quick absorption. Edibles have a delayed onset (30-90 minutes) and longer duration (4-8 hours) because THC undergoes first-pass metabolism in the liver, producing a more potent metabolite (11-hydroxy-THC) that accumulates slowly.
While there is a strong statistical association between cannabis use, especially in adolescence, and the development of schizophrenia, establishing direct causality is challenging. The prevailing view is that cannabis can accelerate the onset and worsen the prognosis of schizophrenia in individuals already genetically or biologically predisposed, rather than causing it de novo.
The terms Indica and Sativa are botanical classifications that do not reliably track with chemical composition or subjective effects. Research suggests that the variability within these classifications is greater than between them, and subjective differences are largely attributed to expectancy bias.
CBD has been clearly shown to be effective in treating specific forms of pediatric epilepsy, such as Dravet syndrome, at very high doses (e.g., 1,500-2,000 mg). However, for other conditions like sleep, pain, or anxiety, there is little conclusive clinical trial data to support significant benefits at the much lower doses typically found in commercial products.
Key health risks include potential lung damage from smoking, possible cardiovascular issues (like tachycardia and vascular stiffness), and a rare but real cyclic vomiting syndrome in heavy users. Cannabis use is contraindicated for individuals with a predisposition to schizophrenia or bipolar disorder.
Cannabis has some mild analgesic properties, but its primary benefit for chronic pain patients seems to be stripping away the emotional component of pain, making it feel like 'background noise.' This allows patients to sleep better and function more effectively, even if the physical sensation of pain persists.
Many people report using cannabis to reduce anxiety, and some animal and limited human studies suggest lower doses can be anxiolytic. However, higher doses can paradoxically increase anxiety, and its efficacy in clinical trials for anxiety disorders is still being investigated.
Anecdotal reports and small clinical studies suggest that cannabis, particularly THC, can effectively suppress nightmares in individuals with PTSD, which is a significant benefit for improving sleep quality and overall well-being. This may be due to its effects on REM sleep architecture.
19 Actionable Insights
1. Avoid Cannabis with Psychotic Risk
Individuals diagnosed with schizophrenia or bipolar disorder, or those with a first-degree family member having these conditions, should avoid cannabis to prevent triggering or accelerating disease onset and worsening long-term prognosis.
2. Avoid Cannabis with Cardiovascular Issues
Individuals with pre-existing cardiovascular issues should avoid cannabis due to potential risks like tachycardia and vascular effects, which could unmask vulnerabilities or trigger events.
3. Cease Cannabis for Fertility Issues
If struggling to conceive, both males and females should consider cutting out cannabis use, as it may negatively impact sperm quality or overall fertility in some individuals.
4. Avoid Cannabis During Pregnancy
Most people stop cannabis use upon learning of pregnancy; it is advisable to avoid cannabis during pregnancy due to unknown effects on the developing fetus and potential legal ramifications if accidental pediatric ingestion occurs.
5. Secure Edibles from Children
Store THC-containing edibles securely away from children, as accidental ingestion can lead to severe intoxication, emergency room visits, and potential legal consequences for parents.
6. Practice “Low and Slow” Edible Dosing
When consuming cannabis edibles, start with a very low dose (e.g., 2.5-5mg THC) and wait at least 90 minutes for effects to manifest before considering additional intake, as onset is slow and effects can be potent and long-lasting.
7. Exercise Caution with Concentrates
Be extremely cautious with cannabis concentrates (e.g., dabs, distillates) as they can reach 90-98% THC, are difficult to titrate, and can lead to blood THC levels double to triple that of high-potency flower, increasing risks of adverse effects and tolerance.
8. Do Not Increase During Paranoia
If experiencing anxiety or paranoia from cannabis, do not consume more, as this will likely exacerbate the negative experience.
9. Prioritize Unprocessed Whole Foods
Consume the majority of your diet from unprocessed or minimally processed sources to ensure adequate intake of vitamins, minerals, probiotics, and micronutrients, supporting physical and mental health and preventing overeating.
10. Prioritize Electrolyte Hydration
Consume adequate electrolytes (sodium, magnesium, potassium) to prevent diminished cognitive and physical performance, especially upon waking and during physical exercise or hot days when sweating.
11. Control Sleep Environment Temperature
To fall and stay deeply asleep, and to wake up refreshed, ensure your body temperature drops by 1-3 degrees and then increases by 1-3 degrees, which can be achieved by controlling your sleeping environment’s temperature.
12. Seek Expert Online Therapy
Engage in therapy with a licensed therapist to gain insights into emotional and relationship life, understand oneself better, and inspire positive action, ensuring good rapport, emotional support, and directed guidance.
13. Titrate Inhaled Cannabis Carefully
When inhaling cannabis, especially higher potency flower, take small amounts and allow a few minutes for effects to manifest to avoid overconsumption and adverse responses.
14. Consider Edibles for Lung Health
To mitigate risks of lung damage, emphysema, and other issues associated with combustion from smoking cannabis, consider oral routes of administration (edibles).
15. Vaporize Plant Matter to Reduce Harms
If consuming cannabis via inhalation, consider vaporizing plant matter using a device that heats it without combustion, as this avoids harmful combustion byproducts found in smoking.
16. Caution with Oil-Based Vaping
Be cautious with oil-based cannabis vaping products, as their long-term health effects and specific chemical compositions are not well-researched or regulated, potentially leading to unforeseen harms.
17. Avoid Exercise Before Drug Test
If facing a cannabis drug test, avoid intense exercise or weight loss efforts beforehand, as these can release stored THC from fat cells back into the bloodstream, potentially causing a positive test even after abstinence.
18. Skepticism for Low-Dose CBD
Be aware that most reported effects from low-dose CBD products (e.g., 10-20mg) are likely placebo effects, as efficacious clinical doses for conditions like pediatric epilepsy are typically 1500-2000mg, and oral CBD has very poor bioavailability (around 4%).
19. Hot Shower for Cyclic Vomiting
If experiencing cannabis-induced cyclic vomiting syndrome, a hot shower or capsaicin cream application may provide relief, suggesting an interaction with thermoregulation or autonomic balance.
8 Key Quotes
The main role of endocannabinoids is really to regulate plasticity or homeostasis, allow flexibility of circuits to either goose up their activity or ramp it down if they need to, depending on the environment, depending on the experience of the organism.
Dr. Matthew Hill
THC is actually only a partial agonist. It's not even a full agonist at CB1. But it is high affinity.
Dr. Matthew Hill
The problem is when you just blanket activate all the CB1 receptors in the brain indiscriminately, like you do when you consume cannabis with THC, the resulting effect is the intoxicating state.
Dr. Matthew Hill
If someone has schizophrenia, cannabis is contraindicated. Like, you shouldn't be using cannabis if you have schizophrenia.
Dr. Matthew Hill
To me, cannabis is fuel on a fire. So if someone is prone to developing schizophrenia, adding cannabis into the mix, I think will make it kick in faster and harder.
Dr. Matthew Hill
The biggest predictor of what someone feels when they consume cannabis is what they're told on the label it's going to do to them.
Dr. Matthew Hill
I would argue that the overwhelming majority of the effects of CBD that people report are all placebo effects.
Dr. Matthew Hill
My pain's still there, but now the pain's background noise. So I can sleep at night, and just being able to sleep, I think, is actually providing a huge amount of the benefit to that community.
Dr. Matthew Hill