Teen marijuana use not linked to later depression, lung cancer, other health problems, study finds

Chronic marijuana use by teenage boys does not appear to be linked to later physical or mental health issues such as depression, psychotic symptoms or asthma, according to a study published by the American Psychological Association.

Researchers from the University of Pittsburgh Medical Center and Rutgers University tracked 408 males from adolescence into their mid-30s for the study, which was published in Psychology of Addictive Behaviors.

What we found was a little surprising,” said lead researcher Jordan Bechtold, PhD, a psychology research fellow at the University of Pittsburgh Medical Center. “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.”

Marijuana use has undergone intense scrutiny as several states and the District of Columbia have legalized the drug, prompting the researchers to examine whether teen marijuana use has long-term health consequences. Based on some prior studies, they expected to find a link between teen marijuana use and the later development of psychotic symptoms (delusions, hallucinations, etc.), cancer, asthma or respiratory problems, but they found none. The study also found no link between teen marijuana use and lifetime depression, anxiety, allergies, headaches or high blood pressure. This study is one of just a few studies on the long-term health effects of teen marijuana use that have tracked hundreds of participants for more than two decades of their lives, Bechtold said.

As laws prohibiting marijuana become less punitive, the question, “What about the kids?” becomes more pressing to parents and other adults.

We at the Drug Policy Alliance urge young people to abstain from alcohol, tobacco, and other drugs. We avoid the exaggerations, misinformation and scare tactics of the past. We believe that honesty is the best way to engage youth and the most empowering way to help them make responsible, informed decisions.

Some critics of drug policy reform exploit parents’ worries that legal access to marijuana for adults will make young people more likely to use it. They proclaim that these reforms send the wrong message to kids. They also threaten that adjusting our response to youthful experimentation will inevitably lead teenagers down a path of problematic use and toward more dangerous drugs.

The research was an offshoot of the Pittsburgh Youth Study, which began tracking 14-year-old male Pittsburgh public school students in the late 1980s to analyze various health and social issues. For 12 years, participants were surveyed annually or semiannually, and a follow-up survey was conducted with 408 participants in 2009-10 when they were 36 years old. The study sample was 54 percent black, 42 percent white and 4 percent other races or ethnicities. There were no differences in the findings based on race or ethnicity.

Teen marijuana use not linked to later depression, lung cancer, other health problems Participants were divided into four groups based on their reported marijuana use: 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). Early chronic users reported much higher marijuana use, which rapidly increased during their teens to a peak of more than 200 days per year on average when they were 22 years old. Their marijuana use then declined somewhat as they got older.

The researchers controlled for other factors that could have influenced the findings, including cigarette smoking, other illicit drug use, and participants’ access to health insurance. Since the study included only males, there were no findings or conclusions about women. Relatively few participants had psychotic symptoms, according to the study.

As Marsha Rosenbaum, Ph.D., has noted in her seminal publication, Safety First: A Reality-Based Approach to Teens and Drugs, “…predictions aside, the most reliable information ultimately will come from large scientific surveys of actual substance use, rather than speculation. But since sound research takes years to complete, it has been too early to determine actual prevalence in states that have already legalized. The closest approximation for predicting the impact of legalization, has been the hard data available on teen marijuana use since medical marijuana laws were passed.”

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,” Bechtold said.


Article: “Chronic Adolescent Marijuana Use as a Risk Factor for Physical and Mental Health Problems in Young Adult Men;” Jordan Bechtold, PhD, and Dustin Pardini, PhD University of Pittsburgh Medical Center; Theresa Simpson, MA, and Helene R. White, PhD; Rutgers University; Psychology of Addictive Behaviors; published online Aug. 3, 2015.

How Many Adolescents Use Marijuana?

Marijuana is the illicit drug most likely to be used by teens in the U.S. According to the 2012 Monitoring the Future (MTF) Study, 45.3% of U.S. 12th graders reported having used marijuana once or more in their lifetime, with 22.9% reporting use in the previous 30 days.

In our state, the 2012 Washington State Healthy Youth Survey reported that approximately 19% of students in the 10th grade and 27% of students in the 12th reported current marijuana use, almost double the percentage who smoke cigarettes.  Fewer students in grades 8, 10, and 12 perceive a great risk of harm in using marijuana regularly, and among 10th graders, that percentage dropped from 65% in 2000 to 46% in 2012.  More than half of Washington’s 10th graders report it is easy for them to get marijuana.

Nationally, while the proportion of students using marijuana decreased from 2011-2012, use was still relatively widespread among secondary school students, particularly older males, and more students are using marijuana daily than they were five years ago (daily use among 12th graders increased from 5.1% to 6.5%).

Contact: Jordan Bechtold at .(JavaScript must be enabled to view this email address) or (949) 291-7520.

The American Psychological Association, in Washington, D.C., is the largest scientific and professional organization representing psychology in the United States. APA’s membership includes more than 122,500 researchers, educators, clinicians, consultants and students. Through its divisions in 54 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance the creation, communication and application of psychological knowledge to benefit society and improve people’s lives.

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