Teen Cannabis Use Linked to Higher Risk of Serious Mental Health Conditions

A large new study suggests that teenagers who use cannabis may be more likely to develop serious mental health conditions in early adulthood, including psychotic disorders and bipolar disorder. The findings add to growing evidence that cannabis use during adolescence could have lasting effects on mental health.

Researchers followed more than 463,000 adolescents aged 13 to 17 until they reached the age of 26. The study, published in JAMA Health Forum, found that teenagers who reported using cannabis within the previous year were significantly more likely to later develop psychotic disorders, bipolar disorder, depression, and anxiety.

The strongest associations were seen for psychotic and bipolar disorders, with the risk of both conditions approximately doubling among young people who had used cannabis.

Importantly, cannabis use was typically reported between 1.7 and 2.3 years before a psychiatric diagnosis, strengthening the evidence that cannabis exposure during adolescence may contribute to the later development of mental illness.

Looking beyond heavy cannabis use

Unlike many previous studies, the researchers did not focus solely on heavy cannabis use or cannabis use disorder. Instead, they examined any self-reported cannabis use during the previous year, using information collected through routine screening during paediatric healthcare visits.

Lead author Dr Kelly Young-Wolff said: "Even after accounting for prior mental health conditions and other substance use, adolescents who reported cannabis use had a substantially higher risk of developing psychiatric disorders, particularly psychotic and bipolar disorders."

She added:

"This study adds to the growing body of evidence that cannabis use during adolescence could have potentially detrimental, long-term health effects. It's imperative that parents and their children have accurate, trusted, and evidence-based information about the risks of adolescent cannabis use."

A changing cannabis landscape

Cannabis remains the most commonly used illicit drug among teenagers in the United States, with use increasing throughout adolescence. At the same time, cannabis products have become considerably more potent, with some products containing very high levels of THC, the main psychoactive component of cannabis.

The researchers say these changes make understanding the potential health impacts of adolescent cannabis use increasingly important.

Study co-author Dr Lynn Silver said:

"As cannabis becomes more potent and aggressively marketed, this study indicates that adolescent cannabis use is associated with double the risk of incident psychotic and bipolar disorders, two of the most serious mental health conditions."

She added that the findings point to "the need for an urgent public health response, one that reduces product potency, prioritises prevention, limits youth exposure and marketing and treats adolescent cannabis use as a serious health issue, not a benign behaviour."

What the findings mean

The researchers also found that cannabis use was more common among adolescents enrolled in Medicaid and those living in more socioeconomically disadvantaged neighbourhoods. They suggest that increasing commercialisation of cannabis could widen existing inequalities in mental health outcomes if these trends continue.

As with all observational research, the study cannot prove that cannabis directly causes psychiatric disorders. However, its large sample size and long follow-up period provide some of the strongest evidence to date that cannabis use during adolescence is associated with an increased risk of serious mental health conditions later in life.

The findings reinforce the importance of providing young people and their families with clear, evidence-based information about the potential risks of cannabis use during adolescence.