Researchers from the University of Pittsburgh Medical Center and Rutgers University tracked 408 males from adolescence into their mid-30s.
“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.”
Participants were divided into four groups based on their reported marijuana use: low or non-users (46%); early chronic users (22%); participants who only smoked marijuana during adolescence (11%); and those who began using marijuana later in their teen years and continued using the drug (21%). 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.
“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.
Bill Condie is a science journalist based in Adelaide, Australia.
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