Drug 'doubles mental health risk'
2005-03-01
Smoking cannabis virtually doubles the risk of developing mental illnesses such as schizophrenia, researchers say.
The New Zealand scientists said their study
suggested this was probably due to chemical changes in the brain which resulted
from smoking the drug. The study, published
in the journal Addiction, followed over 1,000 people born in 1977 for 25
years.UK mental health campaigners said it was more evidence of a
drug-induced mental health crisis.
The researchers, from the University of Otago,
interviewed people taking part in the Christchurch Health and Development Study
about their cannabis use at the ages of 18, 21 and 25. They
were also interviewed about various aspects of their mental health. The
scientists found psychotic symptoms were more common among cannabis users. They analysed their findings to take into account
the possibility illness encouraged people to use more cannabis, rather than the
drug contributing to their condition. But
the researchers said the link was not likely to be due to people with mental
illness having a greater wish to smoke cannabis. Instead,
they said cannabis may increase the chances of a person suffering psychosis by
causing chemical changes to the brain. The
researchers also took into account factors such as family history, current
mental disorders, and illicit substance abuse.
'Growing evidence'
The scientists, led by Professor David Fergusson,
said it was likely cannabis use increased the chances of a person suffering
psychosis by causing chemical changes to the brain. Writing
in Addiction, he added: Even when all factors were taken into account,
there was a clear increase in rates of psychotic symptoms after the start of
regular use. These findings add to the
growing body of evidence from different sources, all of which suggest that heavy
use of cannabis may lead to increased risk of psychotic symptoms and disease in
susceptible individuals.
Paul Corry, of the mental health charity
Rethink, said: This is the latest in long line of international research
over the last 12 months that shows we are facing a drug-induced mental health
crisis. Rethink is renewing its call
to the Health Select Committee to investigate the latest research into the link
between cannabis use and severe mental illness. We
need action from the Department of Health and we need it now if we are to avoid
the risk of tens of thousands of young people developing a severe mental illness
in the future.
The Department of Health has said it will review
all academic and clinical studies linking cannabis use to mental health
problems.
Related Links:
http://www.addictionjournal.org/
(Source: BBC News, March 1, 2005)
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