Mat Hayward /

In 1884, a young researcher named Sigmund Freud was studying the mysteries of the human brain when he wrote an article about cocaine. The scientist extolled its benefits in a paper, “Über Coca,” chronicling how he felt when he used the drug. For the next 12 years, Freud habitually used cocaine as he wrote some of his most influential works, including his theories about the Oedipus complex, psychoanalysis, and the unconscious mind.

Many people think that Freud was abnormal. Conventional wisdom implies that smarter people are less likely to use drugs. But a study from Cardiff University in Wales found that people with higher IQs are more likely to indulge in illegal drugs than people of average or lower intelligence.

Researchers surveyed 7,900 British people born in April 1970.

At age 5 and 10, researchers measured their IQs and at 16 and 30, the researchers asked them to fill out surveys about psychological problems and drug use. By age 30, 35% of men and 16% of women admitted to smoking pot at least once in the past year, while 9% of men and 4% of women indulged in cocaine. People who copped to doing drugs also scored higher on IQ tests than those who did not partake.

Women in the top third of IQ scores were five times more likely to have used marijuana or cocaine than those ladies in the bottom third. Men with the highest IQs were almost 50% more likely to use amphetamines and 65% more likely to have used ecstasy.

Lead researcher, James White, provides several theories explaining why smarter people might indulge in drug use more frequently. He says that anti-drug campaigns often provide simple messages that might not appeal to smarter children. Also, bright people may experience more boredom and social isolation than their less intelligent peers. However, he thinks that attitudes might account for the differences:

"The likely mechanism is openness to experience," White told, "and, I think, it's also this idea of having an educated view of risk as well."