A study published by the American Psychological Association this should alleviate some of the worst fears.
Researchers from the University of Pittsburgh Medical Center and Rutgers University studied 408 males from adolescence to their mid-30s. The participants fell into four groups: those with no use or low use of marijuana, early chronic users, those who only smoked during their teens and those who began using it later and continued using the drug. The early chronic users smoked a great deal -- a peak of more than 200 days per year on average when they were 22 years old.
The researchers found no links to physical or mental health issues -- including depression, psychotic symptoms or asthma -- in any group, even those with very high use. They controlled for cigarette smoking, other drug use, access to health insurance and other factors.
"What we found was a little surprising," lead author Jordan Bechtold, a research fellow at the University of Pittsburgh Medical Center, said in a statement.
Based on other studies in the past that seemed to allude to marijuana use and later development of psychotic symptoms such as delusions or hallucinations, the researchers had thought they might find some associations to disease or other health conditions. But there were none.
They also found no link to a wide range of other health issues: cancer, asthma, respiratory problems, depression, anxiety, allergies, headaches or high blood pressure.
Bechtold said he wanted to "help inform the debate about legalization of marijuana" but that this is a very complicated issue and one study, including his own, should not be taken in isolation and should be viewed in context of other studies on teenagers' marijuana use.
