The National Academies 2017 cannabis review: substantial evidence for psychosis risk, little for psychiatric benefit
A National Academies committee graded nearly 100 conclusions. Substantial evidence linked cannabis use to schizophrenia and other psychoses. Evidence for treating anxiety or PTSD was limited, and for depression it pointed to no effect.
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: Mostly associations, not causal findings; published 2017, so later trials and cohorts are not weighed.
The most-cited weighing of cannabis evidence, read conclusion by conclusion for mental health in both directions.
Significant findings
In January 2017 an ad hoc committee of the National Academies of Sciences, Engineering, and Medicine published The Health Effects of Cannabis and Cannabinoids, with "nearly 100 conclusions", each graded on a fixed scale from conclusive to no evidence. On harms, the committee found "substantial evidence of a statistical association between cannabis use and: The development of schizophrenia or other psychoses, with the highest risk among the most frequent users (12-1)". It found moderate evidence of an association with "Increased symptoms of mania and hypomania in individuals diagnosed with bipolar disorders (regular cannabis use) (12-4)", "A small increased risk for the development of depressive disorders (12-5)", "Increased incidence of suicidal ideation and suicide attempts with a higher incidence among heavier users (12-7a)", and "Increased incidence of social anxiety disorder (regular cannabis use) (12-8b)".
On treatment, evidence was "limited" for "Improving anxiety symptoms, as assessed by a public speaking test, in individuals with social anxiety disorders (cannabidiol) (4-17)" and for PTSD symptoms with nabilone, from "one single, small fair-quality trial (4-20)". There was limited evidence that cannabinoids are ineffective for "Reducing depressive symptoms in individuals with chronic pain or multiple sclerosis (4-18)".
The other direction
The same committee found moderate evidence of "Better cognitive performance among individuals with psychotic disorders and a history of cannabis use (12-2a)" and moderate evidence of no association with worsening negative symptoms of schizophrenia (12-2c). It found no evidence either way on cannabis and the course of depressive disorders (12-6) or the development of PTSD (12-10). Outside psychiatry it found conclusive or substantial evidence of benefit for chronic pain in adults, chemotherapy nausea (oral cannabinoids) and patient-reported MS spasticity. Almost every harm conclusion is an association, not proof of cause, and the review is now nine years old.
What this does not show
It does not show cannabis causes psychosis in any one person, or that it treats any psychiatric condition. It is not advice to start or stop anything.
Worth asking
If cannabis helps me sleep or calm down, how would I notice if it were feeding anxiety, low mood or unusual thoughts?
Source
The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research — National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana (2017)
Read the source: https://doi.org/10.17226/24625
DOI: 10.17226/24625
How this was scored
- Study design
- not recorded
- Funding
- not recorded
- Published in
- not recorded
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
We have not finished checking this source, so there is no scoring to show yet. “We have not checked this yet” and “this is disputed” are different statements, so no scored band is shown rather than a low one.
Read the full scoring rubric, including what it can't tell you.
Published October 21, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "not yet assessed". We have not finished checking this source. No judgement either way. One caveat travels with that badge: Mostly associations, not causal findings; published 2017, so later trials and cohorts are not weighed. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research — National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana (2017). DOI: 10.17226/24625. The full source is linked on this page so you can read it yourself.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.