They found that smarter people, that is, people with higher IQs are more prone to do stupid things, BUT, they realize that they are doing these things and seek to counterbalance this. For instance, if a person with a high IQ eats an entire pie, they are proven more likely to go to the gym after to work of the fat they had just gained than those with lower IQs. so, inherently when smart people do drugs, they do things that will repair their bodies as opposed to less intelligent people who will do the drug and not do anything beneficial for their body.
Story Here: http://www.psychologytoday.com/blog/the-scientific-fundamentalist/201010/why-intelligent-people-use-more-drugs
