Two new studies report an increased risk of psychosis among smokers of not only marijuana, but tobacco, too.

The tobacco study has now been published in the journal Acta Psychiatrica Scandinavica, and the marijuana study — which was conducted by the same team — has now been published in The British Journal of Psychiatry.

Research has found links between psychosis and both tobacco and marijuana smoking — particularly in regard to schizophrenia-related psychosis.

However, the precise reasons why people who experience psychosis are more likely to smoke are not clear.

Some scientists think that smoking might act as a kind of "self-medication" — that is, people with psychosis might find that smoking relieves their symptoms, perhaps due to some unidentified neurological mechanism.

Or, smoking might help to make people who have psychosis less bored or stressed, which could also alleviate symptoms.

Recently, studies have started to investigate whether smoking itself might increase a person's risk of psychosis. Although much research has looked at whether smoking marijuana might contribute to an increased risk of psychosis, comparatively few papers have applied the same investigative approach to tobacco.

Marijauna use linked to psychosis risk

In the study of marijuana, the team found an increased risk of psychosis among teenage users.

"We found that young people who had used cannabis at least five times had a heightened risk of psychoses during the follow-up, even when accounting for previous psychotic experiences, use of alcohol and drugs, and the parents' history of psychoses," notes study co-author Antti Mustonen.

"Our findings are in line with current views of heavy cannabis use, particularly when begun at an early age, being linked to an increased risk of psychosis," he adds.

"Based on our results, it's very important that we take notice of cannabis-using young people who report symptoms of psychosis. If possible, we should strive to prevent early-stage cannabis use."