A new study suggests that children with high IQs are linked with illegal drug use, in both adolescence and adulthood (and specifically in their thirties).

The results of the study were published in the Journal of Epidemiology and Community Health.

The research was conducted to better understand the relationship between children and illegal drug use. The investigators worked around recent reports that have linked children with high IQs to excess alcohol intake and dependency.

The conclusion was based on data collected from approximately 8,000 individuals in the 1970 British Cohort Study, a large and ongoing population-based investigation that examines educational qualifications and lifetime drug use, as well as socioeconomic factors. The drugs participants were questioned on included cocaine, cannabis, LSD (acid) and heroin.

The data also included information on measures of lifetime cannabis and cocaine use, social class of parents and psychological distress at 16; this was by way of comparison with drug use over the previous 12 months, educational qualification and gross monthly income at 30. All cohort members had their IQs measured between the ages of 5 and 10.

Confidential psychological distress and drug use surveys were made for each participant, at 16 and 30. Assessed drugs included cannabis and cocaine, while for the most recent survey of thirty-year-olds, amphetamine and ecstasy were included as part of the investigations.

Lead researcher, Dr. James White, Cardiff University and his team showed that by the age of thirty, one in three men and one in six women had used marijuana in previous years. Cocaine use was around 8.6 percent in men and 3.6 percent in women, with a similar pattern of use for other drugs.

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, said 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.

Results showed that IQ scores at 5 were positively associated with cannabis and cocaine; IQ scores at 10 years were positively associated with cannabis and cocaine at age 30. Associations were stronger in women than in men and were independent from psychological distress in adolescence and life-course socioeconomic position.

With regard to intelligence, data suggested that men who showed high IQ scores at 5 were approximately 50 percent more likely to have taken ecstasy and other drugs 25 years later, compared to men with low IQ scores. Women with a high score were found to be twice as likely to have used cocaine and cannabis later in life compared to those with low scores.

The study also discovered that the same associations appeared between participants who received a high score at 10 and subsequently submitted to multiple drug use, although this last connection was only apparent when they were thirty.