Adolescent marijuana use greatly increases the chance of mental illness


According to Harvard Medical School, adolescents who regularly smoke marijuana are twice as likely to develop psychosis or schizophrenia as adolescents who do not light up. Young people who regularly use drugs place themselves at greater risk for developing not just psychosis but a variety of later-life mental health problems.

Early marijuana use and mental health

The Harvard study notes that adolescents with a family history of psychosis have a 1 in 10 chance of developing the disease, but adolescents who add marijuana to the mix double those odds to 1 in 5. The study results agree with results from the seminal study that documented the drug use of 50,000 Swedish soldiers. This study followed these subjects for 15 years, starting when they were teenagers. The study found the soldiers who smoked marijuana at least once were twice as likely to develop schizophrenia as those who never lit up. Soldiers who smoked more than 50 times were six times as likely to develop the disorder.

The ever-developing adolescent brain

The human brain is not fully developed until age 24. When young people use drugs, they interrupt the development of their brain chemistry. The Substance Abuse Mental Health Services Administration’s Treatment Episode Data Set found a significant correlation between early drug use and later health problems, including mental health conditions. Johns Hopkins Bloomberg School of Public Health notes cocaine and amphetamines zero in on dopamine neuro receptors in the brain. Repeated use of these drugs can damage these areas of the brain, leading to poor impulse control in adulthood.

According to, researchers are not in total agreement regarding what happens to the adolescent brain as it matures. What they can agree on is an adolescent brain addled by drugs is at greater risk for developing disease than a nonaddled brain. Compounding the danger, says researchers at the University of Pittsburgh, is that the adolescent brain is naturally more inclined toward risk-taking behavior. Adding drugs to the chemical mix only heightens the desire to walk on the wild side. Researcher Bita Moghaddam refers to this as the disease state. She says, “Most of us turn into perfectly normal adults, but in some individuals this transition may not happen normally, it may under-correct or over-correct, and that’s when disease could happen.”

A specter is haunting later-life mental illness

And that specter is adolescent drug use, says the National Institute of Mental Health. Referring to a 2005 study, “National Comorbidity Survey Replication”, mental illness typically manifests in youth. Young people with incipient mental illness often resort to drugs and alcohol to mitigate the effects of their disorders. In a chemically induced vicious circle, these individuals find they need more and more just to feel normal or to fit in. All the while, their brains are pickling in a contaminated chemical stew. If they continue to use into adulthood, their chances of developing later-life depression, schizophrenia and host of other mental illnesses increases exponentially.

White River Academy is a boarding school and mental health center that specializes in treating young men ages 12 to 17 who have problems with substance abuse or have mental illness. Contact the 24/7 helpline listed on our website to learn more about how we involve your entire family in your son’s recovery. If your son is having problems, we will help.

About the author:

Darren Fraser, worked two and half years as reporter and researcher for The Yomiuri Shimbun until they realized he did not read, speak or write Japanese and fired him. Undeterred, he channels his love of research into unearthing stories that provide hope to those dealing with addiction and mental illness. Darren loves the Montreal Canadiens hockey club and horror films and would prefer to enjoy these from the comforts of his family’s farm in Quebec. 

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