People with high IQs are more likely to smoke marijuana and take other illegal drugs, compared with those who score lower on intelligence tests, according to a new study from the U.K. It’s counterintuitive,” says lead author James White of the Center for the Development and Evaluation of Complex Interventions for Public Health Improvement at Cardiff University in Wales. “It’s not what we thought we would find.”
At age 30, about 35% of men and 16% of women said they had smoked marijuana at least once in the previous year; over the same time period, 9% of men and 4% of women said they had taken cocaine. Previous-year drug users tended to have scored higher on IQ tests than non-users.
The IQ effect was larger in women: women in the top third of the IQ range at age 5 were more than twice as likely to have taken marijuana or cocaine by age 30, compared with those scoring in the bottom third. The men with the highest IQs were nearly 50% more likely to have taken amphetamines and 65% more likely to have taken ecstasy, compared to those with lower scores.
And these results held even when researchers controlled for factors like socioeconomic status and psychological distress, which are also correlated with rates of drug use.
So why might smarter kids be more likely to try drugs? “People with high IQs are more likely to score high on personality scales of openness to experience,” says White. “They may be more willing to experiment and seek out novel experiences.”
“The likely mechanism is openness to experience,” White concludes, “and, I think, it’s also this idea of having an educated view of risk as well.” (Of course, American views about what consists of an “educated” perspective on drug risks have often clashed with those of the more relaxed position typically taken in Europe.)
The study didn’t look at the risk of addiction among those with high IQs because it wasn’t able to measure the frequency of drug use in participants. However, earlier research has found a connection between high IQ and greater risk of alcohol abuse and dependence.
That could potentially be linked to the boredom and social isolation experienced by many gifted children, the authors note. But since a link between IQ and drug use remains independent of psychological distress, that can’t be all that’s going on. “It rules out the argument that the only reason people take illegal drugs is to self medicate,” says White.
The research was published in the Journal of Epidemiology and Community Health.