In 2023, researchers working with the National Institute on Drug Abuse (NIDA) estimated that as many as 30% of schizophrenia cases among men aged 21 to 30 in Denmark might have been prevented by preventing cannabis use disorder. That figure surprises a lot of parents, especially at a time when cannabis is legal in many states and widely seen as harmless.
It doesn't mean that most young people who use cannabis will develop psychosis. They won't. But it does mean the link is real enough that parents of older teens and young adults should know what to watch for, and what to do if something seems off.
What psychosis is
The National Institute of Mental Health (NIMH) describes psychosis as a set of symptoms in which a person has lost some contact with reality. That can include seeing or hearing things others don't, or holding strong beliefs that aren't based in fact.
According to NIMH's 2023 guide, Understanding Psychosis, it often begins in the late teens to mid-20s, which is exactly the age when many young people are experimenting with cannabis. NIMH estimates that between 15 and 100 people out of every 100,000 develop psychosis each year.
There's no single cause. NIMH points to a combination of genetic risk, differences in brain development and exposure to stress or trauma, and lists misuse of alcohol or drugs among other possible factors, along with sleep deprivation and some prescription medicines.
What the Danish study found
The 2023 study, led by Carsten Hjorthøj and published in Psychological Medicine, used national health records covering more than 6.9 million people in Denmark over five decades. NIDA Director Nora Volkow was a coauthor.
According to NIDA's summary, the researchers estimated that in 2021 about 15% of schizophrenia cases among men aged 16 to 49 may have been avoidable by preventing cannabis use disorder, compared with about 4% among women. In men aged 21 to 30, the estimate rose to as high as 30%.
The researchers also found that the share of schizophrenia cases linked to cannabis use disorder had risen steadily over the decades. They connected this to more potent cannabis and more diagnosed cannabis use disorder.
A few cautions matter here. These are population estimates from statistical models, and they describe an association across a whole country rather than a guaranteed outcome for any individual. The study looked specifically at cannabis use disorder, meaning problematic, heavy use, not occasional use. And the researchers say more work is needed to understand why young men appear more vulnerable.
Early warning signs
One of the most useful things a parent can do is know what early changes can look like. NIMH notes that behavior often shifts before full psychosis develops. Signs include:
- Becoming unusually suspicious or uneasy around others
- Trouble thinking clearly or concentrating
- Pulling away from friends and family
- Changes in sleep
- Losing interest in self-care or hygiene
- A sudden drop in grades or job performance
Any of these can also come from stress, depression or the ordinary ups and downs of young adulthood. The concern grows when several appear together, when they're new, or when they keep getting worse.
Talking with your young adult
Conversations about cannabis go better when they're about health rather than rules, especially once a child is over 18. A few approaches help:
Lead with what you've noticed. "You haven't seemed like yourself lately, and you're barely sleeping" opens more doors than "You're smoking too much."
Share the information, not a lecture. Many young people haven't heard about the link with psychosis, particularly with high-THC products. Present it as something you learned and wanted them to know.
Ask about potency and frequency. Daily use of strong concentrates, vapes or edibles carries different risks from the occasional joint.
Mention family history. If a relative has had schizophrenia, bipolar disorder or psychosis, that's worth discussing openly.
Keep the door open. One conversation rarely settles it. Staying connected matters more than winning the argument.
If you're worried
NIMH emphasizes that early treatment often leads to better recovery. Coordinated specialty care, a team-based approach, is the standard of care for early psychosis, and outcomes are better when it starts as soon as possible.
If you notice warning signs, start with a doctor or mental health professional. NIMH also points families to the SAMHSA Early Serious Mental Illness Treatment Locator and the NAMI HelpLine at 1-800-950-6264.
Sometimes the cannabis use itself becomes a problem that needs its own support, whether or not psychosis is involved. For young adults, that might mean outpatient counseling or, when use is heavy and hard to control, a more structured program. Providers vary widely in what they offer; one nonprofit campus in South Texas, for example, lists addiction care ranging from detox to outpatient and aftercare. If mental health symptoms are also present, ask any provider how they handle both together.
If someone is in crisis or having thoughts of suicide, call or text 988. In a life-threatening emergency, call 911.
Staying informed, not alarmed
Most young people who try cannabis will never experience psychosis. But the risk isn't zero, it appears higher with heavy use and potent products, and it falls during the very years when young people are most likely to experiment. Knowing the signs, and talking about them early, is one of the most practical ways parents can help.
Sources
- National Institute on Drug Abuse. Young men at highest risk of schizophrenia linked with cannabis use disorder (news release, 4 May 2023), summarizing Hjorthøj C. et al., Psychological Medicine, 2023, doi:10.1017/S0033291723000880. https://nida.nih.gov/news-events/news-releases/2023/05/young-men-at-highest-risk-schizophrenia-linked-with-cannabis-use-disorder
- National Institute of Mental Health. Understanding Psychosis (NIH Publication No. 23-MH-8110, revised 2023). https://www.nimh.nih.gov/sites/default/files/documents/health/publications/understanding-psychosis/23-MH-8110-Understanding-Psychosis.pdf
- Cenikor. Corpus Christi (client page; read October 2026). https://www.cenikor.org/locations/corpus-christi-texas/
