Does Intelligence Protect Against Mental Illness?
A new study says yes
A fascinating new paper by Magnus Nordmo and colleagues sheds fresh light on a long-debated question: What’s the relationship between intelligence and mental health?
Plenty of studies have tackled this question over the years, but this one is particularly impressive. For one thing, the sample was exceptionally large - nearly 300,000 Norwegian men, all of whom underwent mandatory military IQ testing in late adolescence. For another, mental health diagnoses came from medical records rather than self-reports, boosting the reliability of the data. Finally, the researchers used a clever design that allowed them to assess whether family background explained the association between intelligence and mental health.
The headline result is this: Higher intelligence at age 18 predicted a significantly lower risk of psychological disorders two decades later, between the ages of 36 and 40. The only exception was affective psychosis (which embraces mania and bipolar disorder), which showed no clear relationship with intelligence. For every other disorder, however - from depression to PTSD to drug abuse - smarter teens were more likely to grow into mentally healthy adults. The graph below shows how strong the association was for each of the disorders studied.