Smoking pot may hasten onset of mental illness

[herbsandhelpers]

Smoking pot may hasten onset of mental illness

(Reuters Health) - Smoking marijuana has been linked with an increased risk of mental illness, and now researchers say that when pot smokers do become mentally ill, the disease starts earlier than it would if they didn't smoke pot.

This means that serious psychiatric diseases that might not have shown up until kids were in their teens or twenties - or might never had developed at all - are starting in children as young as 12 who smoke marijuana.

The link between using pot and developing serious mental illness is strongest in the youngest smokers - 12- to 15-year-olds, or kids even younger, said Dr. Matthew Large in an interview with Reuters Health.

"We have to (tell) people who have marijuana in their pockets not to give it to younger people," said Large, who headed up the research at the University of New South Wales in Sydney, Australia.

Large and his colleagues looked at thousands of patients with psychotic disorders like schizophrenia. People with psychotic disorders lose touch with reality -- usually starting in adolescence or young adulthood.

The authors of the new study found that in the subjects who had been pot smokers, the psychotic symptoms began nearly 3 years earlier than in those who had not been marijuana users.

People with schizophrenia often have hallucinations (they see things that aren't there) and delusions (they're often convinced something improbable is true, when it isn't); they also tend to have unusual or bizarre behavior, social problems, and general difficulty in coping with life. According to the National Institute of Mental Health, approximately 2.4 million American adults, or about one in every 100 people over age 18, have schizophrenia.

The vast majority of young people who use marijuana don't develop psychosis. And so far, no one's been able to prove that smoking marijuana actually causes psychotic disorders like schizophrenia, but the new research adds to "growing evidence" that it does, at least in some people, said Dr. Michael T. Compton at George Washington University Medical Center in Washington, DC, who worked on the study.

A number of studies had already suggested that people develop schizophrenia at a younger age if they've been using pot - even if they weren't heavy users -- but not all researchers agreed.

To get a better sense of the evidence, Large and Compton and their colleagues systematically combined and analyzed data from 83 studies involving more than 22,000 people with psychotic disorders like schizophrenia: 8,167 who used marijuana or other substances, and 14,352 who did not.

"Those who used marijuana had an earlier age at onset of the disorder, by (about 32 months) on average, than those who had not used marijuana," Compton said in e-mail to Reuters Health.

Why was there disagreement in the past over whether this effect really exists? The reasons lie in the way the individual studies might have been done, the researchers say in their article, published in the Archives of General Psychiatry.

In their larger analysis, they made sure to account for several factors that authors of the individual studies might not have considered. For example, psychosis develops earlier in boys than in girls - but Large and Compton found that even when they adjusted for that difference, the pot smokers still developed psychotic symptoms earlier.

Also, older people are less likely to be smoking pot than younger patients, so if the individual studies had different proportions of various age groups, the results might have been skewed. Taking that factor into account, the researchers still found that marijuana users developed mental illness at a younger age.

They also tried to see whether their findings could be explained by the year the research was done (because pot may have become more potent over time), whether the research had been done according to good scientific principles, and whether the investigators had defined the start of mental illness according to the date it was diagnosed instead of the date the symptoms started (the date symptoms started is more accurate). But they kept coming back to the same result: people with psychotic disorders who smoked marijuana had symptoms of mental illness at a younger age than those who didn't use pot.

Source: Reuters