Your chance of developing psychosis after smoking cannabis could be down to your genes, scientists have claimed.

Researchers from the University of Exeter and University College London have identified a single gene which they believe shows someone is at a higher risk of suffering from hallucinations, delusions and mental health issues after using the class B drug. This gene – AKT1 – is found in almost half of the population.

The research team discovered that young people with the AKT1 gene experienced psychotic-like symptoms including paranoia and visual distortions more strongly than those without the gene.

The study, which was published in the journal Translational Psychiatry, involved 442 healthy volunteers who had admitted to using cannabis. The participants were given the drug in laboratory conditions and then tested for symptoms of psychosis.

The people were then tested again seven days later when sober and those with the AKT1 gene were found to be at a higher risk of developing permanent symptoms of psychosis.

Around 1% of cannabis users develop psychosis and it is already known that smoking the drug on a daily basis doubles a person’s chance of developing a psychotic disorder. This research could now help doctors to identify those who are most vulnerable to mental health issues triggered by cannabis use.

Users with AKT1 genotype are more vulnerable

One of the report’s authors Celia Morgan, Professor of Psychopharmacology at the University of Exeter, said: “These findings are the first to demonstrate that people with this AKT1 genotype are far more likely to experience strong effects from smoking cannabis, even if they are otherwise healthy. To find that having this gene variant means that you are more prone to mind-altering effects of cannabis when you don’t have psychosis gives us a clue as to how it increases risk in healthy people.

“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. Although cannabis-induced psychosis is very rare, when it happens it can have a terrible impact on the lives of young people.”

The study also found that women were more likely to suffer short term memory loss after smoking cannabis than men.

Professor Morgan said: “Animal studies have found that males have more of the receptors that cannabis works on in parts of the brain important in short term memory, such as the prefrontal cortex. We need further research in this area, but our findings indicate that men could be less sensitive to the memory impairing effects of cannabis than females.”

Drug testing can help identify whether someone is misusing cannabis. AlphaBiolabs offers hair strand tests which can look at an individual’s substance misuse over a period of months, depending on the length of the sample.

This can be useful for employers to identify potential problems among their staff and for family members who want to find out whether a loved one has been abusing illegal drugs.