Cannabis Use Was Not Linked to Worse Outcomes in Youth at High Risk for Psychosis
A 2023 study of adolescents and young adults at clinical high risk for psychosis found no evidence that continued recreational cannabis use was associated with worsening symptoms, neurocognitive performance, social functioning, or treatment patterns over two years. The findings, however, do not show that cannabis is protective or safe for young people at elevated risk.
Published in Psychiatry Research, the study analyzed 210 participants from the Early Detection and Intervention for the Prevention of Psychosis Program. Participants were between 12 and 25 years old, with a mean age of 16.54, and had been identified as being at clinical high risk for psychosis.
The researchers examined cannabis use over a two-year period and compared participants’ clinical symptoms, neurocognitive performance, social and overall functioning, and medication use. They reported that participants who continued to use cannabis had higher neurocognitive and social-functioning scores over time than non-users. They also had lower medication use, while clinical symptoms improved during the follow-up period.
Those results should be interpreted as associations, not evidence that cannabis caused better cognition, improved functioning, or symptom relief. The study was observational and did not randomly assign participants to use cannabis. Differences between users and non-users—including baseline functioning, treatment engagement, or other personal and clinical factors—could help explain the findings.
The study also does not establish that cannabis prevents psychosis or that it had no effect on individual participants’ risk of developing a psychotic disorder. Its narrower conclusion was that, within this clinical-high-risk sample, patterns of recreational cannabis use were not associated with the adverse two-year outcomes the researchers evaluated.
The findings add to a mixed research literature. A separate prospective study that followed 334 people at clinical high risk for psychosis for two years likewise found no significant association between baseline cannabis use and transition to psychosis, persistence of symptoms, or functional outcome. An umbrella review of systematic reviews and meta-analyses published in 2023 concluded that an association between cannabis use and transition to psychosis among people at clinical high risk could not be confirmed, while also finding links between cannabis use and psychosis-related outcomes in other populations.
Studies examining cannabis policy have also produced largely null findings for some population-level measures. Research using emergency-department data from Ontario and Alberta found no statistically significant change in presentations for cannabis-induced psychosis or schizophrenia-related conditions after Canada’s first phase of legalization, although cannabis-induced psychosis presentations had increased over the longer period studied. A U.S. analysis of privately insured and Medicare Advantage claims similarly found no statistically significant increase in psychosis-related diagnoses or antipsychotic prescriptions associated with state cannabis policies. These studies examined policy changes and health-care records, not whether cannabis is safe for an individual adolescent.
That distinction is especially important for young people. The Centers for Disease Control and Prevention’s guidance on cannabis and teens notes that adolescent cannabis use has been linked with temporary psychosis and longer-term mental-health problems, with stronger associations reported among people who begin using earlier or use more frequently. More broadly, the evidence varies by age, frequency of use, THC potency, personal vulnerability, and the outcome being measured.
In short, this study challenges the claim that recreational cannabis use inevitably worsens short-term clinical or cognitive outcomes among all young people at high risk for psychosis. It does not support cannabis as a treatment, demonstrate that it improves mental health, or rule out risk for particularly vulnerable individuals. Further longitudinal research is needed to clarify how cannabis use, underlying psychosis risk, treatment, and other factors influence one another.
