In a risk/benefit analysis for cannabis most people don’t realize that adolescents and young adults obtain no benefits from cannabis use, although they are the most likely to be harmed by regular or high-dose use. Adolescence and young adulthood are also life stages when suicidal behaviors, mood disorders, and substance use disorders may cluster.
Key points : Youth often use cannabis to self-medicate, only worsening paranoia and underlying psychiatric vulnerabilities. For teens and young adults, medicinal cannabis has no proven benefits but its use engenders major risks. High-THC exposure correlates highly with increased anxiety, dysphoria, psychosis, and cannabis use disorder.
Harvard’s Kevin Hill et al. (American Journal of Psychiatry) and UCLA’S Michael Hsu et al. (JAMA, 2026) have each highlighted an increased vulnerability to adverse psychiatric and substance use outcomes among adolescents and young adults using cannabis. Hill and colleagues emphasized that cannabis use—particularly early, frequent, or high-potency use—is linked with worsening anxiety, depression, bipolar disorder, and psychotic illness. Hsu and colleagues concluded that randomized trial evidence did not support the routine use of cannabis for acute/chronic pain or insomnia. The authors also associated high-potency cannabis with subsequent psychotic symptoms and noted that nearly a third (29%) using cannabis for medical purposes met the criteria for cannabis use disorder.
Two new analyses published in Lancet Psychiatry and JAMA Internal Medicine make additional key psychiatric points. Jack Wilson and colleagues in Australia performed a systematic review and meta-analysis of randomized trials of cannabinoids for mental disorders and substance use disorders. In this largest-ever review of the safety and efficacy of medicinal cannabis across a range of mental health conditions, published in Lancet, the researchers found no evidence that cannabis effectively treated anxiety, depression, or PTSD. They concluded that medicinal use of cannabinoids for these conditions is rarely justified.
Devan Kansagara and colleagues added in JAMA that there were substantial adverse effects with cannabis. They concluded that THC-predominant cannabis does not improve PTSD symptoms and that there is insufficient evidence of beneficial effects on anxiety, depression, and ADHD. The review emphasized that THC-predominant cannabis carried substantial mental health risks, including worsening mania and function in bipolar disorder and increased psychotic symptoms in psychotic-spectrum disorders. They warned that it’s important for clinicians to understand the lack of clear benefits of cannabis for mental health conditions and the potential for substantial adverse effects.
Cannabis Risks in Adolescents
Young-Wolff’s new research study in JAMA Pediatrics tracked nearly a half-million adolescent Kaiser Permanente Northern California members. They were screened for substance use in routine care and followed into young adulthood. Past-year adolescent cannabis use was associated with increased risks for psychiatric diagnoses, including psychotic disorders, bipolar disorder, depression, and anxiety. The strongest associations were for psychotic and bipolar disorders. Higher-frequency cannabis use was also associated with greater risk compared with any use, suggesting a dose-response relationship. Cannabis use was documented approximately 1.7-2.3 years prior to the first recorded psychiatric diagnoses.
This important data remind me of an analysis of nationally representative survey data from 280,000-plus U.S. young adults age 18-34 in JAMA Network Open by Nora Volkow and colleagues which found that cannabis use correlated with a higher prevalence for suicidal ideation, suicide planning, and suicide attempts. These associations were observed across levels of use, including nondaily use, daily use, and cannabis use disorder, and presented in individuals with and without major depressive episodes. The associations were particularly strong in women.
Finally, these studies are consistent with a huge Danish nationwide cohort study of 6.6 million individuals published in JAMA Psychiatry showing that risks of developing cannabis use disorder (CUD) included an increased risk of developing depression and bipolar disorder. In addition, risks increased for psychotic and nonpsychotic unipolar depression and bipolar disorder. CUD itself was associated with nearly double the risk for depression and a 2-3 times higher risk of developing bipolar disorder in men and women.
Psychosis Risks with Cannabis
Incidence of first-episode psychosis with cannabis use is strongly age-dependent, with a peak between ages 15-30. Males tend to present earlier (late adolescence to early 20s), while females often show a slightly later peak. Some psychosis findings may be a result of attempts to self-medicate psychosis-spectrum symptoms.
Importantly, psychosis exists along a spectrum. Subclinical psychotic-like experiences (PLEs) are relatively common in adolescence, with prevalence estimates of 5-10%, although most do not progress to clinical disorder. However, the persistence and severity of such symptoms are predictive of later psychotic illness.
For psychosis specifically, the risk profile is best understood as developmental, dose-related, and potency-sensitive. The JAMA Internal Medicine review summarized youth literature by stating regular use of high-THC products by adolescents and young adults is linked with a 2-fold to 11-fold increased risk of psychosis. In addition, a higher risk of cannabis use disorder and self-harm occurred among those with mood disorders. It also explicitly recommended that adolescents and young adults altogether avoid cannabis.
Increasing Potency Has Altered THC Exposure and the Risk–Benefit Profile
Cannabis potency has increased substantially over the past two decades, with typical THC concentrations rising from 3-5% in the 1990s to 15-20% or higher today. Concentrates like dabs and oils often reach 60-90% THC. This increase in potency represents a larger shift in exposure than changes in the overall prevalence of use or cannabis use disorder.
Higher THC exposure is also associated with increased anxiety, dysphoria, impaired emotional regulation, and greater risk of cannabis use disorder, which itself may exacerbate underlying psychiatric vulnerability.
Legalization and Market Expansion
The expansion of legal cannabis markets, combined with persistent illicit supply, has increased drug availability. Also, the rise of high-THC formulations and frequent use patterns suggest that population-level exposure to risk factors has increased.
Medicinal claims and legal markets increase availability, further normalize use, and facilitate the commercialization of high-THC products.
Young users are more likely to use high-potency products, including concentrates and vapes. These products deliver higher doses of THC per exposure and may facilitate repeated dosing within brief time intervals.
Adolescence is characterized by ongoing brain maturation, which means high THC exposure during this period may disrupt these processes, potentially leading to persistent alterations in neural circuitry.
Conclusion
Evidence for the medicinal benefits of cannabis do not appear to exist, while serious psychiatric risks continue to be proven, especially in teens and young adults. Although questions of individual-level causality remain, the key message is not that cannabis universally causes psychiatric problems. Instead, it is that cannabis use risks are real and severe consequences are increasingly concentrated in young individuals exposed to frequent high-potency cannabis use.
