July 8, 2024 • 3hr 52min
Dr. Matthew Hill: How Cannabis Impacts Health & the Potential Risks
Huberman Lab
Key Takeaways
- Cannabis contains many compounds, but THC is the main psychoactive component responsible for the "high" feeling
- THC acts on CB1 receptors in the brain, which are normally activated by endogenous cannabinoids like anandamide
- Unlike endogenous cannabinoids which act in specific ways, THC broadly activates CB1 receptors across the brain, leading to the intoxicating effects
- People tend to self-titrate cannabis use to achieve similar blood THC levels regardless of potency, except with very high potency concentrates
- There is no clear evidence that cannabis directly causes schizophrenia, but it may trigger or worsen symptoms in those predisposed
- CBD has limited evidence for benefits at typical doses, with most effects likely due to placebo
- Potential harms of cannabis use include lung damage from smoking, cardiovascular effects, and cyclic vomiting syndrome in heavy users
- Potential benefits include pain relief, reduced anxiety, and improved sleep, especially for conditions like PTSD
Introduction
In this episode, Dr. Andrew Huberman interviews Dr. Matthew Hill, a professor and expert on the biology of cannabis. They discuss how cannabis affects the brain, the differences between THC and CBD, potential risks and benefits of cannabis use, and current research on medical applications. Dr. Hill provides a balanced, evidence-based perspective on many aspects of cannabis, clarifying misconceptions and highlighting areas that need more research.
Topics Discussed
Cannabis Basics and How It Works in the Brain (7:16)
Dr. Hill explains that cannabis contains many compounds, but THC (delta-9-tetrahydrocannabinol) is the main psychoactive component responsible for the intoxicating "high" feeling. THC acts primarily on CB1 receptors in the brain, which are normally activated by endogenous cannabinoids like anandamide and 2-AG.
- CB1 receptors are widely distributed throughout the brain
- Endogenous cannabinoids act as a "thermostat" to maintain homeostasis in neural circuits
- Unlike endogenous cannabinoids which act in specific ways, THC broadly activates CB1 receptors across the brain
- This broad activation leads to the intoxicating effects of cannabis
"THC, when you consume it orally or inhalation wise, and it gets into your blood and into your brain, it's just blanket activation. You're just carpet bombing the whole system indiscriminately." - Dr. Matthew Hill
Effects of Cannabis on Appetite, Memory, and Time Perception (33:46)
Dr. Hill discusses some of the common effects of cannabis use:
- Increased appetite ("the munchies") - THC activates circuits involved in feeding behavior and enhances the reward value of food
- Altered time perception - Cannabis can cause time to feel like it's passing more slowly
- Short-term memory impairment - Acute cannabis intoxication can impair short-term memory and recall
He notes that regular users may develop some tolerance to these effects over time.
Routes of Administration and Potency (1:04:09)
Dr. Hill explains the differences between smoking/vaping cannabis versus oral consumption:
- Inhaled cannabis leads to rapid onset of effects (within minutes) but shorter duration
- Edibles have a delayed onset (30-90 minutes) but longer-lasting effects
- People tend to self-titrate cannabis use to achieve similar blood THC levels regardless of potency
- Very high potency concentrates are an exception and can lead to much higher blood THC levels
"The majority of adverse events that happen with cannabis happen with edibles, because people don't understand this. And so they eat a cookie or a gummy. They wait half an hour. Like, I'm not feeling anything. I clearly didn't take enough. And they'll double their dose, and then like 15 minutes later, it starts hitting them." - Dr. Matthew Hill
Cannabis and Mental Health (2:07:05)
Dr. Hill addresses the relationship between cannabis use and mental health conditions:
- There is no clear evidence that cannabis directly causes schizophrenia
- Cannabis use is associated with earlier onset and worse outcomes in those predisposed to schizophrenia
- The relationship may be due to shared genetic/biological factors rather than cannabis causing schizophrenia
- Cannabis can trigger anxiety in some people, especially at higher doses
- Many people report using cannabis to reduce anxiety, but clinical evidence is limited
"My perspective on this is, and I'll explain why I have this perspective and how I justify it, is, 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
CBD and Its Effects (2:57:00)
Dr. Hill discusses cannabidiol (CBD) and its purported effects:
- CBD does not produce intoxicating effects like THC
- High doses of CBD have shown benefits for certain types of epilepsy
- Most commercial CBD products contain very low doses unlikely to have significant effects
- Many reported benefits of low-dose CBD are likely due to placebo effects
- More research is needed on potential benefits of CBD at clinically relevant doses
"I would argue that the overwhelming majority of the effects of CBD that people report are all placebo effects." - Dr. Matthew Hill
Potential Harms of Cannabis Use (3:19:12)
Dr. Hill outlines some potential risks associated with cannabis use:
- Lung damage from smoking cannabis (though less evidence for lung cancer compared to tobacco)
- Possible cardiovascular effects, including increased risk of stroke
- Cyclic vomiting syndrome in some heavy users
- Increased risk of psychosis in those predisposed to schizophrenia
- Potential for developing cannabis use disorder (estimated 30% risk in weekly users)
Potential Benefits and Medical Uses (3:31:30)
Dr. Hill discusses some potential benefits and medical applications of cannabis:
- Pain relief, especially for chronic pain conditions
- Reduced anxiety for some users (though more research is needed)
- Improved sleep, particularly for conditions like PTSD
- Appetite stimulation for cancer patients
- Nausea reduction
He notes that more rigorous clinical research is needed to establish efficacy for many of these uses.
Cannabis and Anxiety (3:40:18)
Dr. Hill discusses his research on how endocannabinoids like anandamide regulate anxiety and stress responses:
- Stress can cause a rapid loss of anandamide signaling in the brain
- This loss of anandamide may contribute to anxiety
- Some people may use cannabis to "fill in the gap" if they have naturally low endocannabinoid levels
- This could explain why many people report using cannabis for anxiety relief
"Maybe some people are trying to fill in a gap of something that's deficient in them and therefore that can help them feel less anxious." - Dr. Matthew Hill
Conclusion
Dr. Hill provides a nuanced, evidence-based perspective on cannabis, highlighting both potential benefits and risks. He emphasizes the need for more rigorous research, especially on medical applications. The discussion clarifies many misconceptions about cannabis and CBD, while also pointing out areas where our understanding is still limited. Overall, the episode provides valuable context for making informed decisions about cannabis use and interpreting claims about its effects.
