Psychiatrists are insisting that cannabis is a significant cause of psychosis. This is despite a Home Office report that only one per cent of schizophrenia diagnoses are cannabis-related.
The Royal College of Psychiatrists said there is a “wealth of research evidence” linking cannabis to psychosis, as well as violence and psychological impairment.
The college added it was “very concerned” about the Home Secretary Charles Clarke’s decision not to reclassify Class C cannabis as a Class B drug.
A report last week by the Home Office’s Advisory Council on the Misuse of Drugs concluded that evidence on cannabis’s mental health links is not strong enough to justify upgrading the drug to class B.
“Current evidence suggests, at worst, that using cannabis increases the lifetime risk of developing schizophrenia by 1%.” said the report.
However, the Royal College of Psychiatrists (RCP) has disagreed with the decision not to reclassify cannabis.
A RCP statement read: “The college is very concerned about the Home Secretary’s decision not to reclassify cannabis.”
Although not specifying whether it disagreed with the advisory council’s “one per cent” figure, the RCP statement read: “Research shows that anyone with a pre-existing mental health problem, or who is more vulnerable to mental illness (e.g. with a family history of schizophrenia), is at increased risk of psychosis and other mental illnesses such as depression, if they use cannabis.
“Acute cannabis intoxification can also lead to short-term memory loss, as well as to poor co-ordination and learning.
“The risks are particularly worrying with the young who are more vulnerable to its damaging effects. Moreover, there is overwhelming evidence that exposure of the unborn child to cannabis is associated with significant cognitive impairment, and behavioural and emotional problems in childhood and adolescence.”
Clarke said his decision was influenced by the fact that cannabis use had fallen by four per cent among 16 to 24-year-olds from 28 per cent in 1998 to 24 per cent last year.
But Clarke said he is to order research into possible links with mental illness and studies into the strength of cannabis most widely used.
A public campaign will also be launched stressing cannabis is harmful and illegal.
Cannabis used to be a Class B drug, and was reclassified to Class C in January 2004.
“Many people wrongly interpreted the reclassification to mean that cannabis was not harmful and that its use was not harmful and that its use was acceptable and even legal,” said Mr Clarke.