A high childhood IQ may be linked to drug use in later life, particularly among women, a new study shows.
Analysis of almost 8,000 people showed that men with a high IQ at the age of five were around 50% more likely to have taken drugs such as amphetamines or ecstasy 25 years later than those with low IQ scores.
Women in the study published in the Journal of Epidemiology and Community Health were more than twice as likely to have used cannabis and cocaine as those with low IQ scores.
The findings did not change irrespective of anxiety or depression during adolescence, parental social class, and lifetime household income.
By the age of 30, around one in three men and one in six women had used cannabis in the past 12 months.
For the same period, 8.6% of men and 3.6% of women had used cocaine.
Other drugs that appeared in the study included uppers, downers, LSD and heroin.
Study author Dr James White said: "Although most studies have suggested that higher child or adolescent IQ prompts the adoption of a healthy lifestyle as an adult, other studies have linked higher childhood IQ scores to excess alcohol intake and alcohol dependency in adulthood."
Although it is not yet clear exactly why there should be a link between high IQ and illicit drug use, the authors of the Cardiff University study point to previous research which shows that highly intelligent people are open to experiences and keen on novelty and stimulation.
Other research has also shown that brainy children are often easily bored and suffer at the hands of their peers for being different, "either of which could conceivably increase vulnerability to using drugs as an avoidant coping strategy", according to Dr White.