Study Finds No Link Between Teen Pot Use and Adult Mental Health Issues

Justin Karter
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A long-term study that followed 408 seventh-graders for over 20 years found no association between marijuana use at a young age and an increased risk of psychosis, depression, and anxiety in adulthood.  The study, published in the journal Psychology of Addictive Behaviors, was led by Jordan Bechtold of the University of Pittsburgh School of Medicine.

“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,” Bechtold said in a statement to the American Psychological Association.

The researchers used data from the Pittsburgh Youth Study, which tracked a cohort of boys from seventh-grade into adulthood.  After being randomly selected from the Pittsburgh public schools in 1987, the participants were interviewed every six months for two and half years until they were roughly 16 years old.  Researchers then interviewed the participants annually for the next ten years and then again, a decade later, when they were about 36 years old.

Of the 408 participants who completed the study 46% were identified as low or non-users of marijuana and the rest were divided between adolescence-limited users (10.7%), late increasing users (21%), and early onset chronic users (22%).  The study found no significant differences in the likelihood of mental health problems between these groups.

The researchers found it “particularly striking”  that there was no difference in the risk of mental health problems between non-users and those in the early onset chronic group who “were using marijuana (on average) once per week by late adolescence and continued using marijuana approximately 3– 4 times a week from age 20 to 26 years.”

The study also investigated how marijuana use may differ in its impact on long-term mental health between African American and Caucasian men. Previous research found that African-American men are “more likely to have health problems and less likely to have access to quality health care services than white men.”  Bechtold and his collaborators studied whether marijuana use might compound these existing inequalities, leading to a greater prevalence of mental health issues, but found that ethnicity did not significantly impact their results.

With political debates about the legalization of marijuana intensifying over the past year, interest in the potential mental health effects of chronic use has increased.  In light of previous research, which has suggested that chronic marijuana use may be tied to deleterious effects, such as early onset psychosis and an increased risk of developing bipolar disorder, Bechtold described the study’s findings as “a little surprising”  but cautioned that marijuana legalization is “a very complicated issue and one study should not be taken in isolation.”

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Bechtold, J., Simpson, T., White, H. R., & Pardini, D. (2015, August 3). Chronic Adolescent Marijuana Use as a Risk Factor for Physical and Mental Health Problems in Young Adult Men. Psychology of Addictive Behaviors. Advance online publication. (Full Text)

 

9 COMMENTS

  1. this is a very important study.

    A few years ago we were constantly told that canabis increased the likelyhood of psychosis in the vulnerable. Yet the traumatic events in the lives of people who developed psychosis were ignored. Now this study says there is no link between canabis and mental illness.

    I think smoking canabis can laeve some people freaked out but if they stop smoking it they should calm down. I see no reason why smoking it should cause long term damage. So this study makes sense to me.

    • “Now this study says there is no link between canabis and mental illness.”

      I can guarantee you that there is. This is a self-evident fact that many people have experienced to such a profound degree, that really even having this link on MIA is going to damage its credibility.

      If I take one hit of weed, as I’ve done several times in the past, I go completely manic. Literally, something straight out of “reefer madness”, talking 2 million miles a minute, face red and sweaty, laughing like a lunatic, unable to finish sentences or string coherent words together E.G. “word salad”, and of course panic attacks are inevitable. From what I’ve gathered from a lot of reading over the years, about one-third of people have the same reaction to weed, albeit to varying degrees. I absolutely never have those “symptoms” otherwise, although profound anxiety issues plagued me for weeks after each exposure to cannabis.

      • JeffreyC

        I agree with the concerns you are raising. My experience working with addiction problems in community mental health tells me that a certain percentage of people are very sensitive to pot and it can trigger uncomfortable and disturbing effects for them.

        Often people’s relationship with the drug changes or evolves over time. Some people’s first experience is very bad and they avoid its use thereafter. For others their early experience may be very pleasant and fun but after a period of time (months or years) these experiences start shifting towards a more paranoid edge with uncomfortable anxiety.

        Richard

      • Wow, JeffreyC, I’ve never seen anyone describe themselves as ‘reefer madness’ stoned like this. When I was in college, we’d watch that movie and laugh at how outrageous it was for being such obvious propaganda. Perhaps I stand corrected! Sounds like something you should definitely avoid, as I imagine it is for some people.

        People react differently to different things ingested–whether natural herbal, like cannabis, or chemical, like pharmaceuticals. Either one can cause really unpleasant and disturbing reactions from side-effects. I know Vicodin makes A LOT of people feel really loopy and incoherent. Both Vicodin and Cannabis are painkillers.

        I live in a county where it’s the #1 industry and medical cannabis is big business. It’s also the most peaceful and grounded, very ‘neighborly’ community in which I’ve ever lived.

        So I still don’t see either correlation nor causation between cannabis and mental health issues, other than what is contingent upon one’s own particular sensitivities. But I don’t see how at all how a general statement can be made like this. I think that’s totally subjective and individual, as with anything at all in life.

        For some, cannabis is extremely beneficial, which is way more than I can say for a lot of substances which are totally legal and commonly used, extremely and dangerously addicting, and do way more harm than good in most people. Cannabis at least really does help a lot of people.

    • “Let’s legalize it already. We can get drunk and smoke cigarettes all we want…”

      By that philosophy, we might as well just legalize everything. Since after all some laws don’t make sense, so then why have any laws at all? I’d rather we ban alcohol and tobacco.

  2. Thank you, longitudinal data, for giving us further evidence to debunk the causal link between marijuana and psychosis. This study is a nice complement to the one that came out of Harvard a few years ago (http://psychcentral.com/news/2013/12/10/harvard-marijuana-doesnt-cause-schizophrenia/63148.html) demonstrating that people with a family history of schizophrenia are more likely to smoke marijuana as a teenager, and after factoring out family history, there was no link between marijuana and subsequent psychosis.