Gifted Issues Discussion homepage Forums General Discussion High IQ and drug use

I haven't heard anyone talking about the fact that the lower your IQ, the less disposable income you are likely to have, and the higher your IQ, the less likely you are to work in any number of jobs (such as driving buses) that have mandatory routine drug testing. I wonder how well these sorts of factors were controlled for in the study? (But I don't wonder enough to get past the paywall...)