Childhood IQ Linked to Drug Use

A recent study published in the ‘British Medical Journal of Epidemiology and Community Health’ shows that drug abuse in adult life is linked to IQ in childhood.  Around eight thousand people from a British cohort study which began in 1970 were followed for thirty years.

At the ages of five and ten, the children took accredited IQ tests and factors such as parental social class and psychological stress were also recorded. Then at sixteen years old the participants were asked about their psychological well being and which drugs they were taking. 

The list comprised of a number of drugs and their alternative names including cocaine, cannabis, LSD, and barbiturates as well as a fictitious drug called Semeron.  Any results that showed a participant had taken Semeron were removed from the study due to possible inaccuracies.

A similar set of questions were asked when the participants turned thirty with a few additions to the drug list including ketamine and ecstasy.  People who had taken three or more of the drugs were labelled as polydrug users.

The results of the study showed that overall a higher IQ score as a child led to an increased likeliness of drug use as a teenager or adult. 

In particular, it was found that by the age of thirty, women that were in the top third for IQ scores were twice as likely to have used cocaine or cannabis as the lower third, while men showed similar results but to a lesser degree.  The higher IQ group were shown to be 83% more likely to take cannabis and 73% for cocaine.

Men were 50% more likely to take amphetamines, ecstasy and be polydrug users by the age of thirty if they were in the high IQ third compared with the lowest third. 

Although cocaine use by sixteen year olds was not high for any IQ groups, girls were 4.6 times and guys 3 times as likely to take cannabis.

A key point of this study was that it took into account other factors that could lead to drug use, such as socio economic status, whether there was any psychological distress in childhood or during the time drugs were taken.

However, the study offers no answers as to why there is a link between IQ and drug use but there has been speculation that it may relate to more expendable income or the availability of drugs at university.