Scientists Tie Low IQ to Disorders

Researchers from the Harvard School of Public Health have concluded that children born with lower IQs possess higher risk of psychiatric disorders, according to a decades-long study of 1000 people in New Zealand. Children with lower IQ levels were more vulnerable to having chronic psychiatric disorders after the age of 32, researchers said.

The study was conducted on a cohort of children born between 1972 and 1973 in Dunedin, New Zealand and first tested at age three.

The participants were assessed for psychiatric disorders at ages 18 through 32 by doctors without any knowledge of the cohort members’ IQ levels or psychiatric history.

“Lower childhood IQ predicted increased risk of schizophrenia, depression, and generalized anxiety disorder,” said lead researcher Karestan Koenen, assistant professor of society, human development, and health at the School of Public Health. “Individuals with lower childhood IQ also had more persistent depression and anxiety and were more likely to be diagnosed with two or more disorders in adulthood.”

Although the exact mechanism through which childhood IQ may be linked to higher risk of adult anxiety disorders is not known, the researchers were capable of suggesting several potential explanations.

In their report, they theorize that lower childhood IQ might suggest varied levels in brain health that make the subject more exposed to certain mental disorders. The researchers further said that people with lower IQ levels find it more difficult to cope with complex modern daily life, possibly making them more vulnerable to developing psychiatric symptoms.

Researchers argue that the findings can be helpful in treating individuals with psychiatric disorders.

“Lower childhood IQ was associated with greater severity of mental disorders including persistence over time and having two or more diagnoses at age 32,” said Koenen. “Since individuals with persistent and multiple mental disorders are more likely to seek services, cognitive ability may be an important factor for clinicians to consider in treatment planning.”

The researchers added, however, that they could not find any correlation between lower childhood IQ and panic disorder, simple phobia, obsessive-compulsive disorder or substance dependence disorders.

For recent research, faculty profiles, and a look at the issues facing Harvard scientists, check out The Crimson's science page.