There are advantages to being smart. People who do well on standardized tests of intelligence—IQ tests—tend to be more successful in the classroom and the workplace. Although the reasons are not fully understood, they also tend to live longer, healthier lives, and are less likely to experience negative life events such as bankruptcy.
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%).
To explain their findings, Karpinski and colleagues propose the hyper brain/hyper body theory. This theory holds that, for all of its advantages, being highly intelligent is associated with psychological and physiological “overexcitabilities”, or OEs. A concept introduced by the Polish psychiatrist and psychologist Kazimierz Dbrowski in the 1960s, an OE is an unusually intense reaction to an environmental threat or insult. This can include anything from a startling sound to confrontation with another person.
Psychological OEs include a heighted tendency to ruminate and worry, whereas physiological OEs arise from the body’s response to stress. According to the hyper brain/hyper body theory, these two types of OEs are more common in highly intelligent people and interact with each other in a “vicious cycle” to cause both psychological and physiological dysfunction. For example, a highly intelligent person may overanalyze a disapproving comment made by a boss, imagining negative outcomes that simply wouldn’t occur to someone less intelligent. That may trigger the body’s stress response, which may make the person even more anxious.
The results of this study must be interpreted cautiously because they are correlational. Showing that a disorder is more common in a sample of people with high IQs than in the general population doesn’t prove that high intelligence is the cause of the disorder. It’s also possible that people who join Mensa differ from other people in ways other than just IQ. For example, people preoccupied with intellectual pursuits may spend less time than the average person on physical exercise and social interaction, both of which have been shown to have broad benefits for psychological and physical health.
All the same, Karpinski and colleagues’ findings set the stage for research that promises to shed new light on the link between intelligence and health. One possibility is that associations between intelligence and health outcomes reflect pleiotropy, which occurs when a gene influences seemingly unrelated traits. There is already some evidence to suggest that this is the case. In a 2015 study, Rosalind Arden and her colleagues concluded that the association between IQ and longevity is mostly explained by genetic factors.
From a practical standpoint, this research may ultimately lead to insights about how to improve people’s psychological and physical well-being. If overexcitabilities turn out to be the mechanism underlying the IQ-health relationship, then interventions aimed at curbing these sometimes maladaptive responses may help people lead happier, healthier lives.