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\u2014including schizophrenia, depression, and anxiety\u2014compared to peers using other substances like alcohol or opioids.<\/p>\n
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.<\/p>\n
Key Facts & Statistics<\/p>\n
The Adolescent \u201cVulnerability Window\u201d (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 \u201caccelerates\u201d the onset of mental illness in vulnerable youth, leading to earlier diagnoses and leaving a seemingly \u201clower risk\u201d 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.<\/p>\n
Source: Johns Hopkins University<\/p>\n
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.<\/p>\n
The\u00a0study\u00a0found 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.\u00a0\u00a0\u00a0\u00a0<\/p>\n
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.<\/p>\n
The study was published online March 5 in the\u00a0American Journal of Psychiatry.<\/p>\n
\u201cIs cannabis use a unique risk factor compared to the use of other substances such as alcohol, opioids, or cocaine? That\u2019s the question we addressed in this study, and our findings suggest that that relative risk depends on the user\u2019s age,\u201d says study co-author\u00a0Johannes Thrul, PhD, associate professor in the Department of Mental Health at the Bloomberg School.<\/p>\n
Products made from the\u00a0Cannabis sativa\u00a0plant 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\u00a0in 24 U.S.\u00a0states and the District of Columbia. Surveys suggest daily use of cannabis is higher than alcohol consumption.<\/p>\n
\u201cMuch of our interest in this came from the recent legalization of recreational cannabis in Maryland, in 2023, and other states,\u201d\u00a0says Ryan Nicholson, MD, resident at Johns Hopkins University School of Medicine. \u201cWe wanted to understand cannabis-related psychotic disorders clinicians are seeing in the context of other substance-related psychotic disorders.\u201d<\/p>\n
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.<\/p>\n
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\u2014a condition that implies relatively heavy cannabis use\u2014but had not been diagnosed with other psychiatric disorders.<\/p>\n
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.<\/p>\n
The researchers compared the rates of subsequent schizophrenia and other psychiatric diagnoses in these two patient groups\u2014adults age 18 and older (691,806 patients) and one for those age 17 and under (49,586 patients).<\/p>\n
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.<\/p>\n
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.<\/p>\n
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.<\/p>\n
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.<\/p>\n
\u201cThere 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,\u201d he says.<\/p>\n
One of the paper\u2019s 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.\u00a0<\/p>\n
Key Questions Answered:Q: Is cannabis worse for teens than other drugs like alcohol or opioids?<\/p>\n
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.<\/p>\n
Q: Does this mean cannabis is \u201csafe\u201d for adults?<\/p>\n
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, \u201clower risk\u201d relative to other high-risk substances doesn\u2019t mean \u201czero risk.\u201d<\/p>\n
Q: Does this study prove that cannabis causes schizophrenia in teenagers?<\/p>\n
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 \u201caccelerant.\u201d 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\u2014or at all\u2014without the drug.<\/p>\n
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<\/p>\n
Author: Saznin Mehta<\/a>
Source: Johns Hopkins University<\/a>
Contact: Saznin Mehta \u2013 Johns Hopkins University
Image: The image is credited to Neuroscience News<\/p>\n