29 April 2005
Cannabis-pyschosis link – it’s in the genes
A gene linking teenage cannabis use with psychotic illnesses has been identified in an international study based on data
from the University of Otago’s Multidisciplinary Health & Development Study.
“What we found is those people with a particular version of this gene have almost 11 times the chance of having a
diagnosis of psychosis if they used cannabis during adolescence. The strength of this association is on par with that
seen for a-pack-a-day cigarette smoker and the likelihood of ending up with lung cancer,” Multidisciplinary Health & Development Study director Associate Professor Richie Poulton says.
The paper comes from an international research team from the University of Otago, the Institute of Psychiatry at King’s
College London and the University of Wisconsin and was led by Professors Avshalom Caspi and Terrie Moffitt.
The study, which will be published in the international journal Biological Psychiatry next month, focused on the COMT
gene, which was chosen because it is known to play a part in the production of dopamine, a brain-signaling chemical that
is abnormal in schizophrenia, Assoc Prof Poulton says.
“The findings reinforce a growing consensus that nature and nurture are not mutually exclusive forces but combine to
affect behaviour and health,” he says.
“This explains why cannabis use has a devastating affect on some users but leaves most unharmed. We have suspected
genetic factors are responsible for the difference but until now no gene has been identified.”
The Dunedin Multidisciplinary Health & Development Study has tracked approximately 1000 men and women since they were born in Dunedin in 1972 and 1973, making
it one of the longest and most detailed cohort studies in the world. Each participant was interviewed at 13, 15 and 18
years about cannabis use and tested to determine which type of COMT gene they had inherited and followed up at age 26
for signs of mental illness.
ENDS