The IQ effect was larger in women: women in the top third of the IQ range at age 5 were more than twice as likely to have taken marijuana or cocaine by age 30, compared with those scoring in the bottom third. The men with the highest IQs were nearly 50% more likely to have taken amphetamines and 65% more likely to have taken ecstasy, compared to those with lower scores.
And these results held even when researchers controlled for factors like socioeconomic status and psychological distress, which are also correlated with rates of drug use.

So why might smarter kids be more likely to try drugs? “People with high IQs are more likely to score high on personality scales of openness to experience,” says White. “They may be more willing to experiment and seek out novel experiences.”