IQ correlated with disorders

SciAm reports:

Now there’s some bad news for people in the right tail of the IQ bell curve. In a study just published in the journal Intelligence, Pitzer College researcher Ruth Karpinski and her colleagues emailed a survey with questions about psychological and physiological disorders to members of Mensa. A “high IQ society”, Mensa requires that its members have an IQ in the top two percent. For most intelligence tests, this corresponds to an IQ of about 132 or higher. (The average IQ of the general population is 100.) The survey of Mensa’s highly intelligent members found that they were more likely to suffer from a range of serious disorders.

The survey covered mood disorders (depression, dysthymia, and bipolar), anxiety disorders (generalized, social, and obsessive-compulsive), attention-deficit hyperactivity disorder, and autism. It also covered environmental allergies, asthma, and autoimmune disorders. Respondents were asked to report whether they had ever been formally diagnosed with each disorder, or suspected they suffered from it. With a return rate of nearly 75%, Karpinski and colleagues compared the percentage of the 3,715 respondents who reported each disorder to the national average.

The biggest differences between the Mensa group and the general population were seen for mood disorders and anxiety disorders. More than a quarter (26.7%) of the sample reported that they had been formally diagnosed with a mood disorder, while 20% reported an anxiety disorder — far higher than the national averages of around 10% for each. The differences were smaller, but still statistically significant and practically meaningful, for most of the other disorders. The prevalence of environmental allergies was triple the national average (33% vs. 11%).

This is interesting, but how is it that in 2017, research like this is still being published without a control group?

Maybe Mensa appeals to neurotic people. Maybe neurotic ppl are more likely to respond to these questionnaires. Maybe smart ppl are more likely to self-diagnose with some oddball disorder.

These confounders can be reduced by using a control group. They could have sent out similar questionnaires to a couple of groups that seem similar to Mensa, except for the high IQ admission requirement. It is not that complicated. Social science studies without a control group are usually worthless.