Children with high IQs are more likely to use marijuana, cocaine, amphetamines and other illicit drugs as teenagers and adults, according to new data on nearly 8,000 British men and women who were tracked for more than three decades.
Researchers from Cardiff University and University College London became interested in the question after other studies found that kids who scored high on intelligence tests were more likely than their peers to become heavy drinkers and alcoholics when they grew up. They found one study from the U.S. that suggested high-IQ children were at greater risk of experimenting with drugs only during their teen years, but the study participants were not representative of American kids as a whole (most were African-Americans who lived in Chicago).
For the new study, James White and G. David Batty examined data from the 1970 British Cohort Study, which has tracked thousands of people who were born in the same week of April 1970. Many of these kids took IQ tests at age 5 and/or age 10. As part of the study, participants were asked about their drug use when they were 16 years old and again when they were 30.
Using that data, White and Batty divided the people into three groups based on their IQ scores (low, medium and high). They found that those in the top IQ group at age 5 were more likely than those in the bottom IQ group to have ever used marijuana by the time they were 16. At age 30, women with high IQ scores were more than twice as likely as low-IQ women to have used marijuana or cocaine in the prior year, while men with high IQs were 46% more likely to have used amphetamines and 65% more likely to have used ecstasy than their low-IQ counterparts.