Dutch researchers have found a link between pot use and psychosis among teenagers. They also found that the link may run in the opposite direction: that there is a tie between teenagers with psychotic symptoms and later marijuana use.
"We have focused mainly on temporal order; is it the chicken or the egg? As the study shows, it is a bidirectional relationship," said Merel Griffith-Lendering, the lead author of the Dutch study, in an email to Reuters.
Links between pot and psychosis were established in prior research studies, but scientists wanted to find out if marijuana use increased the risk of mental illness or if those with mental symptoms such as delusions and hallucinations used pot to alleviate their symptoms, Reuters noted.
"What is interesting in this study is that both processes are going on at the same time," Gregory Seeger, medical director for addiction services at Rochester General Hospital in New York who was not involved in the Dutch study, told the newswire service.
Seeger said the adolescent brain is vulnerable, and scientists are concerned about the effects pot can have on young minds.
"That's a very vulnerable period of time for brain development," he said, adding that those with a family history of schizophrenia and psychosis appear to be more affected by the toxic effects of THC, the active ingredient in marijuana.
The Dutch study sought to determine whether psychosis symptoms came first and marijuana use later or if the reverse is more likely.
The study surveyed 2,120 Dutch teenagers. The subjects were asked about their marijuana use at 14-, 16- and 19-years old.
Psychosis vulnerability tests were also administered to gauge the teenagers’ feelings of loneliness and whether they suffered from hallucinations.
About 44 percent of the teenagers, or 940 participants, said they smoked pot, and the study found a “bidirectional link” between pot and psychosis, Reuters reported.
For example, the study found pot use at age 16 was linked to psychotic symptoms at 19, while psychotic symptoms at 16 was linked to pot use at 19.
The study does not prove that smoking pot causes psychotic symptoms, or that psychotic symptoms causes pot use, but the research did find that there is a link between pot and psychosis.
"We can say for some people that cannabis comes first and psychosis comes second, but for some people they have some (undiagnosed) psychosis (and) perhaps cannabis makes them feel better," Maria di Forti, of King’s College in London, told Reuters. Di Forti was not involved in the Dutch study.
Seeger said the public should be more aware about the link between pot and psychosis.
"I think the marijuana is not a harmless substance. Especially for teenagers, there should be more of a public health message out there that marijuana has a public health risk," he said.
Griffith-Lendering echoed that sentiment.
"Given the severity and impact of psychotic disorders, prevention programs should take this information into consideration," she told Reuters.