Cannabis and mental health: psychosis risk, potency and young brains

For some people, cannabis worsens mental health. The risk is highest for the young and the genetically vulnerable, and today's high-THC products are where the danger concentrates. Four Huberman Lab conversations agree on that warning, while disagreeing about how far it goes. The middle ground is that legal is not the same as safe, but cannabis is not a universal cause of madness.

Andrew Huberman, reading from a Lancet Psychiatry review, says heavy use, meaning more than twice a week, is associated with four times the risk of psychosis later in life, particularly for people predisposed to schizophrenia or bipolar disorder. He says higher THC potency brings higher risk, that starting at 12 to 14 more than doubles later psychosis risk, and that adolescent use speeds thinning of the prefrontal cortex. He adds that anxiety relief fades over about a year of chronic use, and that taking more does not fix paranoia. He urges anyone pregnant, breastfeeding or trying to conceive to avoid cannabis, THC and CBD in any form.

Cannabis researcher Matthew Hill agrees on the vulnerable. He says "if someone has schizophrenia cannabis is contraindicated," and would tell anyone with a first-degree relative with schizophrenia or bipolar disorder to avoid it. For them, "cannabis is fuel on a fire": it can bring on a first episode sooner and worsen the outlook. But he disputes that it causes schizophrenia in people who would not otherwise develop it. Schizophrenia rates did not shift as cannabis went mainstream, and genetic studies suggest vulnerability predicts cannabis use more than the reverse. He argues the real potency problem is concentrates, which can reach 90% THC or more and are nearly impossible to dose, while flower users mostly take fewer puffs of stronger product. He says most adverse events with edibles come from taking more before the first dose has kicked in.

Stanford psychiatrist Nolan Williams calls THC pro-psychotic and CBD anti-psychotic, and notes that CBD has been bred out of many strains. He would not want a teenager using cannabis before about 25, though he sees occasional use by a healthy adult as relatively safe for most people. Harvard psychiatrist Chris Palmer says THC acts on receptors on mitochondria, and that heavy adolescent users show shrinkage in brain areas rich in them.

The causation dispute is real, but the positions converge in practice on harm to the vulnerable. Hill also corrected several of Huberman's earlier biological claims, and Huberman accepted several corrections. Hill describes a more mixed picture on anxiety, with low doses calming and high doses provoking it.

What to do with it: check your family history first. Wait until at least 25. Avoid concentrates. Keep frequency low. With edibles, go low and slow and do not redose after half an hour. Never take more to fix a bad reaction. Do not trust indica and sativa labels. Watch for dependence, which Hill says may approach 30% among weekly users.

If you have a personal or family history of psychosis, bipolar disorder, depression or anxiety, or are pregnant, talk with a doctor before using cannabis in any form.