Pubdate: Tue, 20 Dec 2005
Source: Medical Post (Canada)
Copyright: 2005 The Medical Post
Author: Karen Birchard


LONDON - A Danish study has found that almost half of all patients who
are treated for cannabis-induced psychosis go on to develop some form
of schizophrenia. Almost one-third go on to be diagnosed with paranoid

The researchers, writing in the British Journal of Psychiatry, said in
the study, those who used cannabis showed schizophrenic symptoms
earlier than those who were not users.

The team from Aarhus University Hospital said there's been very little
research carried out on people with schizophrenic symptoms who were
known users of cannabis despite knowledge that cannabis has been
linked to mental illness. This study is the first to show that
temporary mental problems due to cannabis use are often followed by
psychiatric illness.

The researchers followed 535 patients for three years. All had been
treated for cannabis-induced psychosis. They were compared with more
than 2,700 people with schizophrenia-spectrum disorders who had no
history of cannabis-induced illness.

Forty-five per cent of the 535 went on to develop schizophrenic
disorders. More than 72% went on to suffer from other mental illnesses
such as depression. Only about 15% required no further psychiatric
treatment after their initial cannabis-induced psychosis.

The researchers then compared the ages when schizophrenic symptoms
were noticed and found the drug users were much younger than those who
hadn't used cannabis.

The men showed symptoms, on average, at 24.6 years, compared with 30.7
years in the comparison group. For women, the age was 28.9 years for
the drug users compared with 33.1 years.