Children with high IQs - and especially girls - are more likely to take illegal drugs in their 30s, new research shows.
Dr James White from Cardiff University examined data from just under 8,000 people in the 1970 British Cohort Study, a large ongoing population based study examining lifetime drug use, socioeconomic factors and educational attainment. Factors such as social class and levels of depression were controlled for.
The IQ scores of the participants were measured at age five and 10. They were asked about levels of psychological distress and drug use at the age of 16, and again at the age of 30. Drugs assessed at 16 included cannabis and cocaine; the second time, amphetamines and ecstasy were added to the list.
By the age of 30, around one in three men and one in six women had used cannabis in the previous year; for cocaine, the figures were 8.6 percent of men and 3.6 percent of women, with a similar pattern of use for the other drugs.
However, men with high IQ scores at the age of five were around 50 percent more likely to have used amphetamines and ecstasy as adults.
The link was even stronger among women, who were more than twice as likely to have used cannabis and cocaine as those with low IQ scores. The same associations emerged between a high IQ score at the age of 10 and subsequent use of cannabis, ecstasy, amphetamines, and cocaine.
"Although most studies suggest 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," says Dr White.
"Although it is not yet clear exactly why there should be a link between high IQ and illicit drug use, previous research has shown that people with a high IQ are more open to new experiences and keen on novelty and stimulation."