Pubdate: Mon, 16 Feb 2015
Source: Guardian, The (UK)
Copyright: 2015 Guardian News and Media Limited
Author: Hannah Devlin, Science correspondent


Smoking powerful "skunk" cannabis triples the risk of suffering a 
serious psychotic episode, scientists have found.

The drug is linked to one quarter of all new cases of psychosis, the 
study revealed.

The findings add to a compelling body of evidence that smoking strong 
cannabis "tilts the odds" towards a person developing psychosis, 
which leads to schizophrenia in about half of cases.

The study found that people who smoked skunk every day had five times 
the normal risk of experiencing extended episodes in which they heard 
voices, suffered delusions or demonstrated erratic behaviour.

Sir Robin Murray, professor of psychiatric research at King's College 
London, said there was clear evidence for a causal link between 
smoking strong cannabis and the risk of mental illness.

Between 2005 and 2011, the scientists worked with 410 patients, aged 
18-65, who presented at South London hospitals with a first episode 
of psychosis and had symptoms such as hearing voices or suffering 
delusions for at least a month. A further 370 healthy participants 
from the same area were included as controls.

The study, published in the journal Lancet Psychiatry, showed that 
cannabis potency and frequency of use were strongly linked to the 
risk of developing mental health problems  factors that the authors 
say doctors often overlook.

Those who reported smoking milder forms of the drug, such as hash, 
did not appear to be at increased risk, for instance.

Murray added that, since 2011 when the study ended, cannabis had 
generally been increasing in potency, with synthetic varieties linked 
to acute episodes of psychosis.
- ---
MAP posted-by: Jay Bergstrom