Children with a low IQ (intelligence quotient) have an increased risk of developing mental health problems such as schizophrenia, depression and generalized anxiety disorder. These are the findings of a study spanning 30 years, and published in the Journal of Psychiatry. Findings were based on a sample of 1,037 children born in 1972-73 in Dunedin, New Zealand.
The association between low IQ and psychiatric disorders is long suspected. IQ is regarded as a kind of cognitive reserve which appears to provide additional resilience and protection from mental health problems. People with higher IQs seem, in general, to be less vulnerable to a range of mental health problems.
In the study, children were first assessed at the age of three and then every two years until the age of 15. Four additional assessments were then made at ages 18, 21, 26 and 32. Psychiatric disorders were assessed between ages 18 to 32 by clinicians who were unaware of the IQ of the person they were evaluating.
Study author and lead researcher professor Karestan Koenen, of the Harvard School of Public Health, said adults with lower childhood IQ have more persistent depression and anxiety and were more likely to be diagnosed with two or more disorders.
Quite what the mechanism is that relates lower childhood IQ with mental health problems in later life, is not really understood. Certain mental health problems, such as obsessive-compulsive disorder, simple phobia or panic disorder, are not associated. Still, the research team speculate that low childhood IQ may indicate that not all is well with the general health of the brain and this increases vulnerability to certain disorders. It may also be the case that people with a lower IQ are less able to manage the complexities of modern-day living and succumb more easily to stress.
The message to health professionals is that people with mental health problems are more likely to seek help on a frequent basis. Professor Koenin suggests that people with lower cognitive abilities may struggle to adhere to treatment advice. If cognitive abilities are assessed early on it may help health professionals to tailor treatment packages that stand a better chance of being followed.