Perhaps the best way to predict whether or not an individual will develop schizophrenia is not a psychiatric analysis but rather an IQ test. A recent study found evidence to suggest that a person's IQ level is the biggest predictor of schizophrenia in those with a genetic predisposition. However, unlike the Hollywood blockbuster A Beautiful Mind, where the lead character was both a genius and schizophrenic, researchers believe that those with a lower IQ are actually at greater risk for the condition.

The study involved 1,204,983 Swedish males who were born between 1951 and 1975. The men’s IQ was assessed at the ages of 18 to 20 years old, and it’s these numbers that were used for the study. As reported by Medical News Today, the team used Cox proportional hazard models, a type of statistical technique, to calculate how IQ influences schizophrenia risk among the general population and among close relatives.

Results showed a clear correlation between IQ and schizophrenia.

"What really predicted risk for schizophrenia is how much you deviate from the predicted IQ that we get from your relatives," explained lead researcher, Dr. Kenneth S. Kendler, MNT reported. If you're quite a bit lower, that carries a high risk for schizophrenia. Not achieving the IQ that you should have based on your genetic constitution and family background seems to most strongly predispose for schizophrenia."

To clarify, simply having a low IQ does not predispose a person for schizophrenia. It’s only when this IQ is factored in with a family history. Also, it was not exactly a low IQ that seemed to dictate if you would develop schizophrenia, but rather if you did not achieve the IQ that was in your genes. The life events or reasons a person possesses a lower intelligence, researchers believe, create the link between schizophrenia and IQ, not simply because a person has a low IQ.

Human intelligence is a rather complex concept to explain. Although those with higher IQ tend to score better on standardized tests, this is not the best way to measure intelligence. According to Encyclopedia Britannica, intelligence consists of a person’s ability to learn from experiences, adapt to new situations, understand and handle abstract concepts, and use knowledge to manipulate his environment.

Intelligence is a largely inherited trait, but there are many factors that influence whether or not a child’s optimal intelligence will be reached. Think of intelligence in comparison to height. A child’s genes may indicate he will grow to be 6 feet tall, but if he does not receive proper nutrition or experiences a serious illness, he may never reach this height.

Thus is the same with intelligence. Factors such as a child’s environment, whether or not he is exposed to drugs, or even a traumatic experience, may make it more difficult for the child to reach his optimal IQ, predicted by his genes. According to Kendler, these non-genetic factors, which also contribute to intelligence, may be the cause for the link between lower IQ and higher risk of schizophrenia.

This study presents an interesting theory, but more research is needed to thoroughly understand the unclear link between IQ and mental health. Schizophrenia is a largely debilitating mental health condition affecting an estimated 2.4 million adults in the U.S. Researchers hope that by understanding its exact causes, they may develop more effective treatments.

Source: Kendler KS, Ohlsson J, Sundquist J, Sundquist K. IQ and Schizophrenia in a Swedish National Sample: Their Causal Relationship and the Interaction of IQ With Genetic Risk. The American Journal of Psychiatry. 2014.

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