Cannabis Use in Adolescence Predicts Higher Risk of Major Depressive Disorder and Suicidal Behavior in Adulthood, Says Psychology Researcher

By Tom McLaughlin

The trend toward legalizing marijuana does not eliminate the potential for harmful side effects brought on by cannabis usage, especially for adolescents, warns a Rutgers University–Camden researcher.

Marmorstein notes that the latest study does not prove that cannabis use causes mental-health issues, but it does show that there is an increased risk for them.

“It’s possible to take a position that is pro-legalization while acknowledging the risks, just as it is valid to be anti-legalization because of those risks,” says Naomi Marmorstein, a professor of psychology at Rutgers University–Camden. “For instance, cigarettes are legal, but they have been proven to be harmful to the body.”

Marmorstein cautions that, based on her latest research, cannabis use in adolescence predicts a higher risk of major depressive disorder and suicidal behavior in adulthood.

“This study does not prove that cannabis use causes these mental-health issues, but it does show that there is an increased risk for them,” she says.

Marmorstein and researchers from the Research Institute of the McGill University Health Centre and the University of Oxford examine the association of cannabis use in adolescence and the risk of depression in young adulthood in a study published in the journal JAMA Psychiatry.

According to the Rutgers–Camden researcher, this new study is a meta-analysis of earlier studies focusing on the association of cannabis use in adolescence and later depression, anxiety, and suicidal behavior. Rather than a review of these prior studies, which is analogous to reading them and concluding what they had determined, the meta-analysis reanalyzed the results from them – looking at more than 23,000 individuals – to determine any associations.

She explains that some prior research had found an association between cannabis use in adolescence and major depression in adulthood, but it still needed to be investigated further.

Marmorstein notes that some prior research had found an association between cannabis use in adolescence and major depression in adulthood, but it still needed to be investigated further.

“The questions still remained: ‘Is this depression because cannabis use can result in experiences that can make you depressed, such as dropping out of school, an inability to keep a job, or getting arrested?” asks Marmorstein. “Or is the depression due to the cannabis use itself?”

In her 2011 study, titled “Explaining Associations between Cannabis Use Disorders in Adolescence and Later Major Depression: A test of the psychosocial failure model,” Marmorstein showed that even in the absence of psychosocial failure – defined as educational problems, such as high school dropout; occupational problems, such as persistent unemployment; and criminal activity – there is still an association between cannabis use in adolescence and depression in adulthood.

The new study published in JAMA Psychiatry extends Marmorstein and other researchers’ prior work by analyzing results from their studies, resulting in findings that are more robust and applicable to diverse individuals and communities.

The Rutgers–Camden researcher notes that, although the new study still doesn’t prove causality, it is important for people to be informed of the potential damaging effects of cannabis use in adolescence – no different than the side effects listed on the label for medication.

“We don’t know if the side effects are caused by the medication, but we are saying that they are more common among people who take this particular medication,” she says. “Using that same standard, you would say that depression and suicidal behavior are more common among adults who used cannabis as an adolescent than those who didn’t.”

Marmorstein adds that, although their study didn’t address the point directly, early initiation to a variety of psychoactive substances shows a concerning link to a range of mental health issues that may follow. Furthermore, she says, because teenage brains are still developing, it is possible that the effects of various substances can be stronger on adolescents’ brains than those of adults.

“Delaying onset of use is good from both of these perspectives,” she says.

Posted in: Research Highlights

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