In the study of close to 8,000 people, those who had high IQs when they were aged 5 and 10 were more likely to use certain illicit drugs at age 16 and at age 30.
The findings appear online in the Journal of Epidemiology and Community Health.
Exactly why having a high IQ at age 5 or 10 may encourage future drug use is not fully understood. But researchers have a theory. "People with a high IQ have also been found to be more open to new experiences," says study researcher James White, PhD, in an email.
White is a research associate at the Center for Development and Evaluation of Complex Interventions for Public Health Improvement at Cardiff University, Wales.
The research has been mixed on how a high childhood IQ affects behavior in adulthood, White says.
"Previous studies have found high childhood IQ is associated with mostly healthy behaviors in adult life, such as having a healthy diet, being physically active, and not smoking," he says. "However, other studies have found high childhood IQ is linked to excess alcohol intake and alcohol dependency in adult life."
Kids With High IQs
In the study, women with high IQ scores at age 5 were more than twice as likely to have used marijuana and cocaine by age 30 than those with lower IQs at age 5.
Men with high IQ scores at age 5 were about 50% more likely to have used speed (amphetamines), 65% more likely to have used ecstasy, and 57% more likely to have used multiple illicit drugs by age 30, compared with those who did not perform as well on IQ tests at age 5.
The findings held when IQ was measured at age 10.
Parents' social status, psychological distress during adolescence, and their adult socioeconomic status did not affect risk of illicit drug use.
The study was not designed to determine how often participants used illicit drugs. More study is needed before researchers can draw any conclusions on how to keep brainy kids from using illicit drugs in the future, White says.
Bruce Goldman,director of substance abuse services at the Zucker Hillside Hospital of the North Shore-LIJ Health System in Glen Oaks, N.Y., says the message to parents of honor roll students is clear.
"Don't be lulled by your kid's good academic performance to think that they are not experimenting with drugs," he tells WebMD. "It is commonplace with peers and it is naive to think that because you have a good, smart kid that they will not be curious."
In fact, they may even be more curious and more apt to seek stimulation than other children, he says. "These kids may be more prone to want to find things out for themselves."