Problem cannabis use is genetic: study
Problem cannabis use is overwhelmingly the result of genes rather than upbringing or lifestyle, a new twin study carried out by the Norwegian Institute of Public Health has concluded.
The study of 1,791 twins from the US state of Virginia found that genetic factors accounted for roughly 79 percent of problem cannabis use, compared to just 54 percent for cocaine.
The shared environment in which those surveyed grew up -- which accounted for as much of 16 percent of cocaine abuse -- seemed to have no bearing at all on the likelihood of someone developing problems with cannabis.
"The factors that explain why some get addicted and others don't are hereditable," the study's author Eivind Ystrøm told The Local. "There's not a single cannabis gene, but if both your parents were cannabis abusers, you would be more likely to have a large number of genes which put you at risk."
Ystrøm said that while at present there was no way to test for vulnerability, he believed those whose relatives have problems with cannabis should be wary of trying the drug.
"If you have a first degree relative that abuses any drug, or has been addicted to any drug, that's the best genetic test that you're going to get today," he said. "That shows you a lot about your own risk."
Shared environment had a large bearing (56 percent) on the likelihood that someone would try cannabis, but not on the likelihood that they would then go on to develop problems.
Ystrøm added that there was a large overlap between the genetic predisposition to become addicted to cannabis and and problems with cocaine and stimulants.
"It turns out that the genetic factors were non specific, so it was the same genes that gave risk for dependence on all the three drugs, so that tells us that it's not actually the drug per se that's addictive, but there's something further up the system, something more related to personality."