Photo Credit: Oscar Aguilar
Scientific Frontline: Extended "At a Glance" Summary: Cannabis Use and Youth Psychosis Risk
The Core Concept: Daily cannabis use in young people significantly increases the probability of developing mental health disorders, leaving users up to four times more likely to develop psychosis than non-users.
Key Distinction/Mechanism: The adolescent and young adult brain is actively developing, making it uniquely vulnerable to the psychological impacts of frequent cannabis use, which can trigger severe mental health disorders and dependence rather than alleviating psychological distress.
Major Frameworks/Components:
- Systematic analysis of the comorbidity between frequent cannabis consumption and psychiatric disorders like psychosis, bipolar disorder, depression, and anxiety.
- Identification of an epidemiological correlation where approximately one in three daily or near-daily users aged 15 to 25 develops cannabis use disorder.
- Evaluation of clinical efficacy, finding no clear evidence that medicinal cannabis successfully treats anxiety, sleep disorders, or depression.
Branch of Science: Psychiatry, Neurobiology, Addiction Medicine, and Epidemiology.
Future Application: Development of integrated, dual-screening clinical approaches that simultaneously address substance use and psychiatric conditions, alongside evidence-based revisions to medicinal cannabis prescribing guidelines.
Why It Matters: Establishing the definitive psychiatric risks of daily youth cannabis usage provides critical guidance for public health policy, early prevention strategies, and clinical treatment protocols for a highly vulnerable demographic.
Young people who use cannabis daily are up to four times more likely to develop psychosis than those who do not, according to an international study led by University of Queensland researchers.
The review analyzed evidence from 17 previous studies to assess whether cannabis use contributed to the development of mental health disorders, including psychosis, bipolar disorder, depression, and anxiety.
Associate Professor Janni Leung from the University of Queensland’s National Center for Youth Substance Use Research said the link between daily cannabis use and psychosis was the strongest and most consistent finding.
“Young people are particularly at risk because their brains are still developing,” Associate Professor Leung said. “This is also the age when cannabis use often begins and when mental health disorders first emerge, which makes young people a key group for prevention.”
Compounding the risk, about one in three people aged 15 to 25 who used cannabis daily or near-daily developed cannabis use disorder, meaning that they struggled to control their use even when it caused harm.
Researchers also found that daily cannabis use may contribute to worsening symptoms of bipolar disorder.
Evidence linking cannabis use to depression and anxiety was less clear, but some of the studies reviewed showed that mental health symptoms improved when people reduced or stopped using cannabis altogether.
The researchers are urging caution among policymakers considering cannabis legislation and among clinicians prescribing potent cannabis products.
“Health professionals should routinely screen for both cannabis use disorder and mental health conditions, given evidence that patients with both have poorer outcomes,” Associate Professor Leung said. “Integrated treatment approaches are needed rather than separate treatment plans that are not always complementary.”
The University of Queensland research team was also involved in a second landmark study, which found no clear evidence that medical cannabis was effective in the treatment of anxiety, sleep disorders, or depression.
“Doctors and other clinicians need to consider the most recent evidence on safety and efficacy when prescribing medical cannabis products. Both reviews highlight that cannabis should not be used as a replacement for more effective mental health therapies,” Associate Professor Leung said.
Additional information: The research was conducted with the University of Bath, Ludwig Maximilian University of Munich, Charlotte Fresenius University, the University of Bristol, King’s College London, the Icahn School of Medicine, and the University of Sydney.
Published in journal: Lancet Psychiatry
Authors: Prof Wayne Hall, PhD, Tesfa M. Yimer, PhD, Rachel Lees Thorne, PhD, Prof Eva Hoch, PhD, Chloe Burke, PhD, Ad Gridley, Prof Yasmin L. Hurd, PhD, Jack Wilson, PhD, Janni Leung, PhD, and Prof Tom P. Freeman, PhD
Source/Credit: University of Queensland
Edited by: Scientific Frontline
Reference Number: psyc061826_01