Summary: New research reveals a striking age-dependent link between cannabis use and mental health. The study found that teenagers with cannabis use disorder (CUD) face a significantly higher risk of developing psychiatric disorders—including schizophrenia, depression, and anxiety—compared to peers using other substances like alcohol or opioids.
Interestingly, the trend reverses in adults, where CUD was associated with a lower risk of psychiatric diagnosis than other substance use disorders. The study suggests that heavy cannabis use may uniquely disrupt the developing adolescent brain.
Key Facts & Statistics
- The Adolescent “Vulnerability Window” (Age 17 and under):
- 52% higher risk for schizophrenia compared to youth with other substance use disorders.
- 30% higher risk for recurrent major depression.
- 21% higher risk for anxiety disorders.
- The Adult Contrast (Age 18 and older):
- 19% lower risk (0.34% vs. 0.42%) of subsequent schizophrenia compared to those with other substance use disorders.
- Overall lower relative risk for psychosis, major depression, and suicide attempts.
- Massive Sample Size: Researchers analyzed nearly 700,000 U.S. medical records, comparing patients with cannabis use disorder (CUD) against matched groups using other substances.
- The Acceleration Theory: The lower risk in adults may be because cannabis “accelerates” the onset of mental illness in vulnerable youth, leading to earlier diagnoses and leaving a seemingly “lower risk” adult population.
- Self-Medication Hypothesis: Researchers also noted that individuals innately predisposed to psychiatric disorders may be more likely to self-medicate with cannabis before their clinical symptoms even appear.
Source: Johns Hopkins University
A new study led by Johns Hopkins researchers found that young people with cannabis use disorder were more likely than young people with other substance use disorders to later be diagnosed with a psychiatric disorder. In contrast, adults with cannabis use disorder were significantly less likely to develop psychiatric disorders, compared to adults with other substance use disorders.
The study found that the relative risk of young people age 17 and under with cannabis use disorder was 52% higher for schizophrenia, 30% higher for recurrent major depression, and 21% higher for anxiety disorders, compared to young people with other substance use disorders. Adults with cannabis use disorder had lower relative risks for being diagnosed with a psychiatric disorder.
The findings highlight the question of whether excessive cannabis use, perhaps more than other substances, might alter brain development of young people, predisposing them to developing a psychiatric disorder.
The study was published online March 5 in the American Journal of Psychiatry.
“Is cannabis use a unique risk factor compared to the use of other substances such as alcohol, opioids, or cocaine? That’s the question we addressed in this study, and our findings suggest that that relative risk depends on the user’s age,” says study co-author Johannes Thrul, PhD, associate professor in the Department of Mental Health at the Bloomberg School.
Products made from the Cannabis sativa plant have been used recreationally in the U.S. since at least the 1800s. Their popularity increased during alcohol prohibition in the 1920s and the counterculture movement in the 1960s. Today, cannabis use by adults age 21 and older is legal in 24 U.S. states and the District of Columbia. Surveys suggest daily use of cannabis is higher than alcohol consumption.
“Much of our interest in this came from the recent legalization of recreational cannabis in Maryland, in 2023, and other states,” says Ryan Nicholson, MD, resident at Johns Hopkins University School of Medicine. “We wanted to understand cannabis-related psychotic disorders clinicians are seeing in the context of other substance-related psychotic disorders.”
The link between cannabis and psychosis first appeared in medical literature in the early twentieth century. In 1987, a study of more than 45,000 Swedish army recruits found that the use of cannabis at the time of conscription was associated with large increases in the risk of subsequent schizophrenia, especially when the cannabis use was heavy. Other studies since then have found similar associations.
For the study, the researchers analyzed nearly 700,000 U.S. medical records from a large commercial database. They identified patients who had been diagnosed with cannabis use disorder—a condition that implies relatively heavy cannabis use—but had not been diagnosed with other psychiatric disorders.
They then matched these patients on measures such as age, sex, ethnicity, and income level, with patients who had been diagnosed with other, non-cannabis substance use disorders and did not have other psychiatric conditions.
The researchers compared the rates of subsequent schizophrenia and other psychiatric diagnoses in these two patient groups—adults age 18 and older (691,806 patients) and one for those age 17 and under (49,586 patients).
The median age among patients with cannabis use disorder was 16 versus 15 among patients with other substance use disorders. About 10% of patients in the cohort of all substance use disorders were under age 12. The authors note that this aligns with reports from adult patients being treated for substance use disorder: 10.2% reported starting substance use at age 11 or younger.
Adults in the cannabis use disorder group had a 19% lower risk (0.34% vs. 0.42%) of subsequent schizophrenia compared to the group with other substance use disorders. Risks of subsequent psychosis, recurrent major depression, and suicide attempts were also lower in the cannabis-use group.
The results are consistent with the idea that heavy cannabis use predisposes young people to subsequent schizophrenia and some other psychiatric disorders that they might not develop otherwise. Thrul notes that this acceleration effect could make these illnesses seem less likely at later ages, thus appearing to lower the risk in adults, at least in relation to other recreational drugs.
Thrul cautions, however, that the causation might point in the other direction, with individuals who are innately more likely to develop certain psychiatric disorders to also have a greater tendency to self-medicate with cannabis, even before their mental health issues have become evident.
“There are still many unknowns on that question, but I would never recommend that teenagers use cannabis, especially not the high-potency cannabis products that are on the market now,” he says.
One of the paper’s limitations is that the database the researchers used relied on International Classification of Diseases ICD-10 coding by other physicians, so the researchers may not know the exact patient history that led to the diagnosis.
Key Questions Answered:
A: According to this study, yes, in terms of psychiatric outcomes. While alcohol and opioids have devastating physical and social costs, cannabis use disorder specifically showed a much higher relative risk for triggering long-term mental health conditions in teenagers.
A: Not necessarily. The study suggests that compared to adults struggling with substances like cocaine or heroin, those with cannabis use disorder had lower rates of psychiatric diagnoses. However, “lower risk” relative to other high-risk substances doesn’t mean “zero risk.”
A: Not definitively, but it strengthens the link. The researchers point to two main theories: either heavy cannabis use uniquely alters the developing adolescent brain, predisposing it to mental illness, or it acts as an “accelerant.” In the second case, a teenager who was already genetically prone to schizophrenia might have their first episode triggered years earlier by cannabis use, whereas they might not have developed it until much later—or at all—without the drug.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this CUD and psychosis research news
Author: Saznin Mehta
Source: Johns Hopkins University
Contact: Saznin Mehta – Johns Hopkins University
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Association of Cannabis Use Disorder Versus Other Substance Use Disorders With Psychiatric Conditions: A Propensity-Matched Retrospective Cohort Analysis” by Ryan C. Nicholson, M.D., M.P.H.; Una E. Choi, M.D.; Ramin Mojtabai, M.D., Ph.D.; and Johannes Thrul, Ph.D. Psychiatry Online
DOI:10.1176/appi.ajp.2025033
Abstract
Association of Cannabis Use Disorder Versus Other Substance Use Disorders With Psychiatric Conditions: A Propensity-Matched Retrospective Cohort Analysis
Objective:
The authors compared the risk of mental disorders between patients with cannabis use disorder (CUD) and those with other substance use disorders (SUDs).
Methods:
The TriNetX Research Network was queried to identify patients with SUDs and no preceding mental disorders and compare 1) adult patients with CUD only versus those with other SUDs, 2) pediatric patients with CUD only versus those with other SUDs, and 3) adult patients with CUD plus another SUD versus those with comorbid noncannabis SUDs. Propensity score matching was performed on demographic characteristics and 24 risk factors or comorbidities. Subsequent diagnosis of schizophrenia and other common mental disorders was assessed.
Results:
Compared to adults with other SUDs, those with noncomorbid CUD (N=345,903 for both cohorts) had a lower risk of schizophrenia (0.34% vs. 0.42%; relative risk [RR]=0.81, 95% CI=0.75, 0.88), depression (1.35% vs. 1.74%; RR=0.78, 95% CI=0.75, 0.81), and psychotic disorders (0.36% vs. 0.52%; RR=0.68, 95% CI=0.63, 0.73). Compared to pediatric patients with other SUDs, those with CUD (N=24,793 for both cohorts) had a higher risk of schizophrenia (0.29% vs. 0.19%; RR=1.52, 95% CI=1.06, 2.19), depression (1.65% vs. 1.27%; RR=1.30, 95% CI=1.13, 1.51), and anxiety disorders (8.13% vs. 6.71%; RR=1.21, 95% CI=1.14, 1.29).
Compared to adult patients with other SUDs, those with CUD and a comorbid SUD (N=203,916 for both cohorts) had a decreased risk of schizophrenia (1.94% vs. 2.25%; RR=0.86, 95% CI=0.83, 0.90), depression (3.98% vs. 5.67%; RR=0.70, 95% CI=0.68, 0.72), bipolar disorder (4.23% vs. 5.60%; RR=0.76, 95% CI=0.74, 0.78), and anxiety disorders (16.20% vs. 21.36%; RR=0.76, 95% CI=0.75, 0.77).
Conclusions:
CUD-associated mental health risks varied by age and comorbid SUDs, possibly due to earlier onset of mental disorders in cannabis users or age-related differences in CUD effects.