Smoking pot as a teen not linked to later depression, lung cancer, study finds

A new study by the American Psychological Association is adding to the great debate over whether marijuana should be legalized: In contrast to some previous research, they found that chronic marijuana use by teenage boys has no apparent link to later physical or mental health issues, including depression or lung cancer.

Researchers from the University of Pittsburgh Medical Center and Rutgers University studied 408 males as part of an offshoot of the Pittsburgh Youth Study, which began tracking 14-year-old male Pittsburgh public schoolers in the late 1980s. The boys were surveyed annually or semiannually for 12 years, and then a follow-up survey was issued at age 36.

Using this information, the researchers then divided the boys into four groups: low or non-users (46 percent); early chronic users (22 percent); participants who only smoked marijuana during adolescence (11 percent); and those who began using marijuana later in their teen years and continued using the drug (21 percent).

Based on results from previous studies, they hypothesized they would find links between marijuana use and the development of certain health conditions in the males—specifically psychotic symptoms (like delusions and hallucinations), cancer, asthma or respiratory problems, lifetime depression, anxiety, allergies, headaches, and high blood pressure. The researchers carefully controlled for other factors that could lead to development of these conditions, including participants’ access to healthcare, cigarette use, and other illicit drug use.

“What we found was a little surprising,” said lead researcher Jordan Bechtold, PhD, a psychology research fellow at the University of Pittsburgh Medical Center, in a statement. “There were no differences in any of the mental or physical health outcomes that we measured regardless of the amount or frequency of marijuana used during adolescence.”

These results were unaffected by race (the group was 54% black, 42% white, and 4% other races or ethnicities), but as the study only tested males, it is uncertain whether the results would differ by sex. And despite the length and size of the study, the researchers made it clear the results are not the end-all be-all for the issue.

“We wanted to help inform the debate about legalization of marijuana, but it’s a very complicated issue and one study should not be taken in isolation,” said Bechtold.

The study was published in the journal Psychology of Addictive Behaviors.

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