Large study finds link between cannabis use in teens and psychosis later

Study design and causation vs. correlation

• Many commenters think the NPR framing overreaches: the underlying paper is about correlation, not proven causation.
• Major concern: excluding teens with diagnosed mental illness doesn’t exclude those already symptomatic but undiagnosed.
• Multiple people argue that only a randomized, blinded trial (cannabis vs. placebo) could really establish causality, and that such a trial is effectively impossible/unethical in teens.
• Some note that cannabis use in teens is still a marker of social “deviance,” making it hard to untangle drug effects from background risk factors.

Predisposition, self‑medication, and confounders

• Common alternative explanation: teens predisposed to mental illness may be more likely to use cannabis, nicotine, other drugs, or engage in other risky behaviors as a form of self‑medication.
• Cigarette smoking’s strong correlation with schizophrenia is cited as a non‑causal analogy.
• Others stress that mental illness, family stress, poverty, trauma, and broader behavioral patterns are all potential confounders that aren’t fully controlled.

Risk size, absolute vs. relative

• Some highlight the reported “2x risk” as large and concerning.
• Others emphasize base rates: ~0.8–1% of the sample developed serious disorders, so the absolute increase in risk may be around 1 percentage point, which could still be compatible with self‑selection.
• A long comment criticizes media and researchers for blurring relative vs. absolute risk and treating triggers in susceptible people as if they create illness in everyone.

Potency, dosage, and modern cannabis

• Several note that today’s cannabis (concentrates, high‑THC strains, edibles) is far more potent, likened to selling only very strong liquor.
• Some describe “micro‑dose” style use (low‑mg edibles, low‑THC vape pens) as a safer, underpromoted pattern vs. heavy daily use.
• Others argue that stronger products don’t automatically mean higher harm if people actually use less—countered by claims that many don’t.

Anecdotes and lived experience

• Multiple anecdotes describe cannabis‑associated psychosis or long‑term cognitive dulling, especially with heavy or early use, convincing some never to touch it.
• Others point out strong survivor bias and self‑selection in such stories and insist that millions use cannabis without severe issues.
• There is broad agreement that cannabis can cause paranoia and acute mental deterioration in some, especially vulnerable individuals.

Legalization, age limits, and politics

• Several argue that even if teen use is risky, that mainly supports 18/21+ age limits, not prohibition.
• Others are firmly against legalization, citing observed harms and what they see as denial and “motivated reasoning” among some pro‑cannabis advocates.
• Opponents are challenged on consistency (alcohol and tobacco policy) and on relying too heavily on anecdotes.
• Some commenters note that both pro‑ and anti‑legalization camps have used exaggerated or misleading claims, which erodes trust and polarizes discussion.

Open questions and suggested research

• Commenters ask about plausible biological mechanisms but note these remain unclear in the thread.
• Suggestions include using legalization as a “natural experiment” (e.g., comparing mental health trends across states over time).
• Overall, many want better‑designed longitudinal studies that more carefully handle predispositions, self‑medication, and social context before making strong causal claims.