5 Min Read

Last Updated: 16.05.23

Effects of Cannabis on Brain & Body

In this episode, Dr. Huberman explains cannabis (aka marijuana), including the biological mechanisms underlying its effects on the mind and body, its known medical applications, its impact on libido, creativity, hunger, hormones, as well as adverse its health consequences.

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Key Takeaways

High level takeaways from the episode.

Do not use cannabis or CBD during pregnancy or breastfeeding — CB1 receptors are an integral part of neural development, present in the newborn and the fetus.

Chronic use of cannabis in 16–24 year olds leads to a higher likelihood of developing depression + anxiety later in life, because the brain is still developing. 4x greater risk of psychosis for those with predisposition to bipolar or schizophrenia.

For those who start using cannabis at 12 or 14, gray matter thins — which is involved in planning & executing plans, organizing life. Some recovery of brain function can be restored by focusing on behaviors that increase brain health.

Even if cannabis use aids in depression or anxiety symptoms in the beginning, over 12 months, levels of anxiety and depression when not under the influence increase in chronic users (more than 2x/week).

Chronic cannabis use disrupts neural circuitry of speech: effects vocal effort and intensity, pronunciation of words and emphasis on particular words, less intonation and anunciation.

Cannabis may enhance creativity by increasing dopamine and divergent thinking, and reducing anxiety.

Generally speaking, smoking more than 2x/week increases prolactin — which lowers libido — and appears to reduce testosterone significantly. Edible cannabis doesn’t seem to have same effect, but research not extensive.

Positive medical uses of cannabis in adults:

Cancer (increase appetite, reduce nausea from chemotherapy)
Glaucoma (reduce intraocular pressure)
Pain reduction.

Smoking or vaping anything severely impairs the function of endothelial cells that make up the brain and body.

Protocols

Science-based tools and supplements that push the needle.

Avoid Cannabis and CBD if Pregnant or Breastfeeding

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Do not use CBD or Cannabis while pregnant or breastfeeding, as it affects CB1 receptors in newborn and fetus.

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CB1 receptors are an integral part of neural development, present in the newborn and the fetus — critical for every aspect of brain wiring and development.

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Avoid Cannabis Before Age 25

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Chronic use of cannabis 16–24 year olds leads to a higher likelihood of developing depression, anxiety later in life, because the brain is still developing.

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Using cannabis at earlier ages can thin gray matter, which is involved in planning & executing plans, and organizing life.

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Making plans and being able to execute plans is fundamental being a healthy human being — the more cannabis one uses, the more impaired those neural circuits are.

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Cannabis Benefits: Appetite, Nausea, Creativity, Pain

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Cannabis for Cancer: can increase appetite and reduce nausea from chemotherapy.

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Cannabis for Glaucoma: can reduce intraocular pressure.

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Cannabis for pain reduction: acts on CB1 receptor.

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Cannabis for creativity: may increase creative thinking by increasing dopamine, reducing anxiety.

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To lower the risk of negative health effects, recommended for above age 25, and less than 2x per week.

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Full Notes

Overview

Cannabis contains over 70 psychoactive compounds and 400 biologically active compounds, most notably THC (tetrahydrocannabinol), CBD (cannabinoid), and CDN (cannabinol)

THC is largely responsible for the psychoactive effects of cannabis (changes in mood, body state, etc.)
CBD has profound effects on the brain and body but without perception of altered mood – CBD doesn’t “get you high”
Sativa strain: creates a head “high” and acts as a stimulant – invigorating, alert, heightened sense of creativity and focus, less susceptible to pain; can be consumed by smoking, edible, sublingual
Indica strain: creates a more full body relaxation, sedative effect; can be consumed by smoking, edible, sublingual
Hybrid strains combine sativa and indica strains to give rise to nuanced brain and body effects
Each strain is further be classified into Type 1 (THC dominant), Type 2 (equal ratios THC:CBD), and Type 3 (CBD dominant) strains based on the ratio of THC to CBD

Brain Receptors

Nicotinic receptors are naturally occurring in the brain and body, binding acetylcholine.

In tobacco, nicotine binds to the nicotinic receptors which have a greater affinity for them, and creates an intense focus that’s not naturally produced in the body.

In a similar way, we have cannabinoid receptors in cells of the brain and body — these cause biological effects on mood, hunger, etc. when the endogenous (internally produced) chemical binds to them.

Marijuana binds to cannabinoid receptors in the brain and body with a much higher potency than our endogenous cannabinoids.

Analog — if you take synthetic estrogen or testosterone, you experience super-physiological effects, it’s not normal.

Endogenous Cannabinoids

Endogenous cannabinoids are released from post-synaptic neurons — this is different from most neurotransmitters, which are released from pre-synaptic neurons.

Endogenous cannabinoids modify the probability that a neuron will release a neurotransmitter.

Endogenous cannabinoids have effects all over the body — on neurons on immune cells, reproductive organs, liver, digestion, hunger, etc.

They regulate the communication between neurons; either increasing or decreasing communication

Two kinds of endogenous cannabinoid receptors:

CB1, in the nervous system
CB2, throughout the body

Cannabis binds to the CB1 receptor — the binding is so strong that it outcompetes the endogenous cannabinoid system.

Effects

Cannabis enters bloodstream within 30 seconds.

Reaches its peak after 30–60 minutes, total duration around 3–4 hours

Cannabis cells are lipophilic — they bind to the fatty membrane around neurons, get into most cells, and remain there for a long time

Detectable in system for ~80 days because of this

Effects of Sativa Strains

Stimulant
Mood elevation
Energetic
‘Head high’
Narrowed sense of focus
Increase CB1 activation
Overall reduction in stress and quieting other circuitry

Effects of Indica Strains

Relaxing
Sedative
Shuts down threat detectors in the brain
Binds to CB1 receptors

Subjective effects and biological reasons

Memory deficit: due to reductions in the electrical activity of the hippocampus, which is responsible for short-term memory
Drop in physical activity: basal ganglia and cerebellum suppressed
Red eyes and dry mouth: reductions in saliva because of CB1/CB2 receptors in eyes + mouth
‘Munchies’: signaling of hypothalamus to the gut, which activates neurons
- Triggers preoccupation with anticipation and taste of food
- Triggers narrowed focus on food
Some anti-pain effects: CB1

Creativity

Most studies don’t delineate between indica and sativa strain.

Two different types of creative thinking:

Divergent thinking — brainstorming or exploring ideas
Convergent thinking — taking loose ideas, synthesizing them into specific framework or coherent idea

Dopamine is closely related to both types of thinking.

High dopamine = more frequent divergent thinking, low convergent thinking
Once you pass a threshold of dopamine, divergent thinking also dips — there’s a sweet spot

Creative process (scientifically, reductionist) involves going into a state where you’re willing to consider a lot of options, disparate or disconnected. Dopamine facilitates this state, where you’re experiencing joy and a pleasure in throwing out all these disparate ideas.

Then when dopamine drops, you start engaging in convergent thinking — narrowing, editing

Some evidence cannabis may enhance creativity

By increasing dopamine and divergent thinking
But could also be explained by the fact that cannabis changes personality of users in a way that taps into the creative process of divergent thinking, rather than impacting the neural circuits themselves
- Cannabis users are more open to new experiences and ways of thinking
- May also reduce anxiety, unlocking a willingness to explore different options

Effects on Speech

Impacts basil ganglia and CB1, which disrupts the neural circuitry of speech.

Effects of chronic use of cannabis on speech:

Change in vocal effort & intensity
Changes in pronunciation of words and emphasis on particular words in a sentence
May read sentences with less intonation and annunciation in their voice

Hormones & Libido

Some individuals experience increase libido with cannabis use, some experience suppressed libido

Dependent on whether cannabis raises prolactin levels in the individual
Generally speaking, smoking more than 2x/week increases prolactin levels, which lowers libido
There’s a subset of people where prolactin is lowered from cannabis smoking, which will increase libido
Edible cannabis doesn’t seem to have same effect on prolactin/dopamine/libido
- Research isn’t extensive enough to draw conclusions

Effects on Hormones from smoking more than 2x/week

Appears to reduce testosterone significantly, elevate aromatase enzyme (enzyme that converts testosterone into estrogen)
Appears to impair sperm motility
Some men experience gynecomastia
Increases cortisol in some, reduces in others
THC is inhibitory for gonadotropin-releasing hormone which ultimately reduces testosterone in men, ovarian health in women

Women should avoid Cannabis and CBD while breastfeeding or pregnant.

CB1 receptors are an integral part of neural development, present in the newborn and the fetus
15% of pregnant mothers report to use cannabis in some form or another — scary statistic

Negative Health Effects

Smoking or vaping anything severely impairs the function of endothelial cells that make up the brain and body.

Chronic Use Increasing Anxiety + Depression

Levels of anxiety and depression, when not under the influence, increase over 12 months in chronic users (more than 2x per week) of cannabis
Over time, requires it higher and higher dosage to elicit the same effects
Anxiety during and outside of drug use gets worse over time
Depression increases over time for people that were not already depressed when they started using
- Cannabis use itself makes people 4x likelier to develop chronic major depression

Risks with Young People + Cannabis

Chronic use of cannabis 16–24 year olds leads to a higher likelihood of developing depression, anxiety later in life, because brain is still developing.

4x greater risk of psychosis for those that have a predisposition to bipolar disorder and/or schizophrenia

For those who start using cannabis at 12 or 14, risk of psychotic episode increases greatly, because of thinning of gray matter — which is involved in planning & executing plans, and organizing life.

Making plans and being able to execute plans is fundamental being a healthy human being — the more cannabis one uses, the more impaired those neural circuits are.
Some recovery of brain function can be restored by focusing on behaviors that increase brain health

- Cardiovascular exercise, adequate nutrition, not smoking nicotine, adequate sleep, weight training, good social connection.

Positive Medical Uses of Cannabis in Adults

Cancer: increase appetite, reduce nausea from chemotherapy
Glaucoma: reduce intraocular pressure
Pain reduction

Study Links

Inspired by Mary Jane? Mechanisms underlying enhanced creativity in cannabis users (Consciousness and Cognition)

Adults with a history of recreational cannabis use have altered speech production (Drug and Alcohol Dependence)

Individual prolactin reactivity modulates response of nucleus accumbens to erotic stimuli during acute cannabis intoxication: an fMRI pilot study (Psychopharmacology)

Bayesian causal network modeling suggests adolescent cannabis use accelerates prefrontal cortical thinning (Translational Psychiatry)

Association of cannabis potency with mental ill health and addiction: a systematic review (The Lancet Psychiatry)

Effects of Cannabis on Brain & Body

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