Cannabis 'ups mental health risk'

Published on 02/12/2004 16:22

FREQUENT use of cannabis during adolescence and early adulthood increases the risk of suffering psychotic symptoms in later life, a new study revealed today.

The study, involving almost 2500 people aged 14 to 24, found the risk of developing symptoms was much higher in young people with a pre-existing vulnerability to psychosis.

Campaigners said the study, published on bmj.com, confirmed the potentially serious health risks linked to cannabis use.

And Scottish Tory justice spokeswoman Annabel Goldie said the findings underlined the folly of taking a softer line on cannabis.

She said: "This study demonstrates the madness of David Blunkett's decision to reclassify cannabis as a 'soft' drug.

"Michael Howard has pledged to change it back to category B and the message must go out that all drugs are dangerous.

"The Scottish government has to stop sending out mixed messages and join us in a zero-tolerance attack on drugs."

Past research into other drugs, including cocaine, has also suggested links to mental illness.

Professor Jim van Os, from the department of psychiatry and neuropsychology at Maastricht University, and his team assessed drug use among 2437 young people.

They also assessed their predisposition for psychosis and psychotic symptoms over a four-year period.

The researchers found that being predisposed to psychosis did not significantly predict cannabis use during the four years.

This went against past suggestions that people may start using cannabis because they are predisposed to psychosis rather than the cannabis causing the psychosis to appear.

The researchers concluded: "Exposure to cannabis during adolescence and young adulthood increases the risk of psychotic symptoms later in life.

"The findings confirm earlier suggestions that this association is stronger for individuals with predisposition for psychosis and stronger for more severe psychotic outcomes."

The researchers also found that the more frequently that cannabis was used, the greater the level of risk of psychosis.

The results of the study were due to be presented today at the Science Media Centre in London.

Cannabis was downgraded from a class B to a class C drug in January, meaning in most cases those found carrying the drug will not be arrested.

Martin Barnes, chief executive of DrugScope, said: "The research underlines that there are potentially serious health risks associated with cannabis use, particularly for young people.

"Frequent use, a predisposition to mental health problems and starting at an early age all increase the risk of adverse affects.

"The challenge is to ensure that messages on cannabis use are understood by teachers and health professionals working with young people and conveyed in ways young people will listen to.

"Shock tactics alone rarely work, but we need to get across that just because you know people who appear to be OK using cannabis, it doesn't mean they are or that it will be OK for you."

Mr Barnes pointed out that after reclassification, which DrugScope supported, cannabis remained an illegal drug.

"Most young people know that cannabis is illegal and harmful, but some may not appreciate what the harms can be," he said.