Link between lower childhood IQ and adult psychiatric disorders
A recent study, which was published in the American Journal of Psychiatry, has discovered a link between lower childhood IQ and adult psychiatric disorders. According to the study mental health disorders including depression and schizophrenia may be predicted by lower childhood IQ. The researchers found that each standard deviation lowering IQ resulted in increased odds of depression (23%) and schizophrenia (42%). The study also found that lower childhood IQ was associated with more severe psychiatric illness. According to Karestan C. Koenen, Ph.D., of the Harvard School of Public Health, and colleagues, “Patients with lower cognitive ability could have difficulty accessing services or difficulty understanding and complying with treatment protocols… These individuals may benefit from interventions aimed at improving mental health literacy.” The following is an excerpt of an article from Medpage Today that discusses the findings more:
Childhood IQ averaged across assessments at ages seven, nine, and 11 years predicted a spectrum of psychiatric disorders at age 32.
With every 15 point increase — one standard deviation — above the mean in childhood IQ, the findings were:
* 42% lower odds of lifetime schizophrenia spectrum diagnosis (95% confidence interval 16% to 59%).
* 23% lower odds of an adult depression diagnosis (95% CI 6% to 37%).
* 26% reduced odds of an adult anxiety disorder diagnosis (95% CI 12% to 38%).
* No difference in alcohol, marijuana, or other drug dependence.
These results generally remained significant after adjustment for potentially confounding factors including childhood socioeconomic status, perinatal problems, low birth weight, and childhood maltreatment, although the association for schizophrenia became nonsignificant (P=0.07).
Higher IQ also appeared to reduce the risk of specific anxiety disorders, including 29% lower likelihood of generalized anxiety disorder (95% CI 8% to 45%) and 40% reduced odds of social phobia (95% CI 23% to 53%).
Although post-traumatic stress disorder and agoraphobia had similar effect sizes as seen for major depression and generalized anxiety disorder, the associations were not significant, likely because of the small number of cases, the researchers said.
Childhood IQ was likewise a significant factor associated with more severe adult psychiatric illness.