They hope this discovery will help identify those who are at risk for drug-induced psychosis.
Plenty of studies have explored the link between smoking marijuana and the onset of psychosis, and recent ones have confirmed that a gene called AKT1 influences the likelihood of marijuana smokers developing a psychotic disorder after prolonged use.
Now, researchers in the UK have taken this link a step further, showing for the first time that this gene also mediates the immediate or acute response to weed in otherwise healthy individuals. In other words, ATK1 can be used to predict which individuals are most susceptible to the mind-altering effects of cannabis.
"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,” said Celia Morgan, a psychopharmacologist from the University of Exeter. “To find that having this gene variant means that you are more prone to mind-altering affects of cannabis when you don't have psychosis gives us a clue as to how it increases risk in healthy people.”
Morgan, along with Val Curran and her team of researchers from University College London, found that young people with a particular variation in ATK1 experienced stronger paranoia, visual distortions, and other psychotic-like symptoms when they were under the influence of cannabis.
The researchers rounded up 442 healthy young marijuana smokers and tested them while under the influence of the drug and again while sober. The scientists measured the symptoms of intoxication and effects of memory loss when the volunteers were “high” and then compared these symptoms with the results of tests taken 7 days later when the users were drug-free.
The volunteers with the AKT1 gene variation were more likely to experience a psychotic response than their cannabis-smoking counterparts who lacked the gene variant. Although previous research had found a higher prevalence of this particular variant of ATK1 in cannabis users with psychosis, it wasn’t known how the gene and psychotic effects tied together.
"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," said Morgan. "Although cannabis-induced psychosis is very rare, when it happens it can have a terrible impact on the lives of young people. This research could help pave the way towards the prevention and treatment of cannabis psychosis."
According to the researchers, about 1 percent of cannabis smokers go on to develop psychosis, and those who smoke every day double their risk. This is because frequent psychotic responses may increase the risk of developing a full-blown psychotic disorder.
In an interesting side finding, the researchers also observed that females are more vulnerable to short-term memory impairment after smoking cannabis than males.
"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,” Morgan said in a press statement. “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.”
The researchers hope that these findings, reported in the journal Translational Psychiatry, will help pinpoint cannabis smokers who are most at risk of developing psychosis. They envision a future genotype-targeted medication that could prevent the onset of a psychotic disorder from recreational cannabis use.