Chronic marijuana use among teenage boys does not appear to lead to later physical or mental health issues — like depression or psychotic symptoms — despite previous research to the contrary, according to a new study.

Researchers at the University of Pittsburgh Medical Center and Rutgers University tracked the progress of 408 males from adolescence into their mid-30s with varying patterns of pot use.

“Overall, data from this sample provide little to no evidence to suggest that patterns of marijuana use from adolescence to young adulthood, for the Black and White young men in the present study, were negatively related to the indicators of physical or mental health studied here,” the psychologists wrote.

The American Psychological Association, the country’s largest organization of psychologists, published the findings Monday in the peer-reviewed quarterly Psychology of Addictive Behaviors.

Based on previous research, lead researcher Jordan Bechtold, a psychology research fellow at the University of Pittsburgh, expected to detect some link between teen marijuana use and the onset of delusions, hallucinations, cancer or respiratory ailments later in life.

“What we found was a little surprising,” Bechtold said in a release. “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.”

Over the past decade, U.S. attitudes and policies toward marijuana have become increasingly liberal. Colorado, Washington, Oregon, Alaska and Washington, D.C., have already legalized the drug for recreational use, and more states are likely to follow.

Given this climate, Bechtold says it is important to empirically evaluate the long-term effects of the plant.

Greg Skipper, director at Promises Behavioral Health, an alcohol and drug addiction treatment center, said the problem with previous studies is that they provided correlation rather than causation data.

Story continues

“It’s hard to get causation data. Does marijuana cause it, or is there another variable that’s sort of linked?” he said in an interview with Yahoo News.

Skipper, a fellow on the American Board of Addiction Medicine, commended the authors of this new study for controlling for variables, like cigarette smoking, to give us a more accurate idea of how marijuana might affect someone over the long term.

“They’re not proving here that marijuana doesn’t have problems, but it may not cause physical illness,” he said. “This is good data. It leads us to thinking that it’s benign in some ways but not other ways.”

Skipper noted that marijuana can cause memory problems and be addictive to some people.

The research team says that the effects on health are just “one piece of the legalization puzzle” and warns against relying upon one study in isolation for this “very complicated issue.”

“This does not discredit the work of others,” the study reads. “It could be the case that cumulative tetrahydrocannabinol exposure, age of initiation of use or use at one particular age is more predictive of negative health outcomes than the overall pattern of use between adolescence and adulthood.”

Mason Tvert, director of communications at the Marijuana Policy Project, which works to end pot prohibition, says the study comes as good news for people on both sides of the marijuana legalization debate.

“Hopefully it will inspire parents, educators and government officials to have a more honest conversation with teens about marijuana,” he said to Yahoo News via email. “Decades of scare tactics and exaggerations about the potential harms of marijuana have failed to prevent many young people from trying it.”

Tvert said it is time for everyone to acknowledge that marijuana is not as harmful as alcohol but that it does pose more potential problems for teens than for adults.

“If they want to try it, they should just wait,” he said.