Your reaction to cannabis 'is hardwired'


Genetics may determine whether THC becomes a problem or not, a new study suggests. Vivian Richter reports.


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Your likelihood of getting stoned may be etched in your DNA. That’s according to a group of UK scientists who have identified a gene which can predict to what extent cannabis users experience the drug’s mind-altering effects – and how likely they are to develop psychotic symptoms.

The finding could help identify cannabis smokers who are most at risk of psychosis, and could help develop gene-based treatments.

Cannabis-induced psychosis is rare, occurring only in around 1% of users. But symptoms, including the loss of touch with reality, can be severe and long-lasting.

Scientists suspected a genetic predisposition to psychosis, but were not sure where in the genome to look for the answer.

In this study, UCL and University of Exeter researchers tested 442 healthy, young cannabis users while under the influence and seven days later, when sober. The team measured intoxication levels and short-term memory loss in both states, and compared the results.

Bad news for female smokers – they are more susceptible to short-term memory loss than males.

To determine what drug dose each user inhaled, study participants dropped a sample of their stash off at a police station, where forensic scientist analysed the samples for THC, the active ingredient in cannabis.

The researchers then sequenced each participant’s DNA for a gene called “AKT1”, which had been linked to psychotic symptoms in previous studies.

The team found participants with a variation in this gene were more likely to experience psychotic symptoms, such as visual distortions and paranoia during cannabis use.

The study also uncovered bad news for female smokers – they are more susceptible to short-term memory loss than males.

Knowing about this AKT1 gene variant will give scientists clues about how cannabis use might increase the risk of psychosis in healthy young people, the authors say.

“Putting yourself repeatedly in a psychotic or paranoid state might be one reason why these people could go on to develop psychosis when they might not have done otherwise,” study author Celia Morgan explained.

“This research could help pave the way towards the prevention and treatment of cannabis psychosis,” she added.

Specifically, the authors hope, the study will not only make it possible to point out who is at risk, but also help develop genotype targeted medication.

The research was published in Translational Psychiatry.

  1. http://www.nature.com/tp/journal/v6/n2/full/tp2015219a.html
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