MedWire News: Smoking cannabis increases the risk of early psychosis symptoms in people at high risk of developing the mental health disorder, research shows.

"Cannabis use is reported to increase the risk for psychosis," explain Dr Cheryl Corcoran, from Columbia University in New York, USA, and team.

But they add that few studies have investigated the effects of cannabis use on symptoms in people at high risk of developing psychosis.

To investigate, the researchers studied 32 patients, aged 25 years or younger, who showed early signs of developing psychosis.

At the start of the 2-year study, all the participants completed questionnaires and underwent interviews and health assessments. They were then monitored for 2 years.

In total, 13 participants reported using drugs such as alcohol, tobacco or cannabis. Indeed, all these patients had a history of cannabis use.

As expected, the researchers found that cannabis users, who tended to be older than the other participants, experienced significantly more anxiety and other cannabis-associated effects than the other participants.

But the team also found that cannabis users experienced more early psychosis symptoms, such as perceptual disturbances, and worse functioning during episodes of increased cannabis use than at other times, and compared with other participants.

The association was not explained by the use of prescription medications and other drugs, notes the team.

"These data demonstrate that cannabis use may be a risk factor for the exacerbation of subthreshold psychotic symptoms, specifically perceptual disturbances, in high risk cases," the researchers conclude in the journal Schizophrenia Research.

They add: "Understanding motivations for [cannabis] use in these vulnerable young people can inform the development of preventive interventions."

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