First, it is important to ask how IQ and health could be connected. Social components are relatively obvious: lower IQ might mean lower level of knowledge about healthy living, for instance. Also, the gradual progression of some chronic diseases may affect cognitive functions leading to lower IQ in unhealthy people. A published analysis showed that long-term sick leave and disability pension are often related to low cognitive abilities. Obviously, this effect is secondary and does not confirm the link between the initial IQ before the disease and the risk of developing this particular disease.
Psychiatric disorders have also long been considered to have a very close link with high IQ. Many geniuses were known to have rather strange or unpredictable characters, suffered from mood disorders and depression. Indeed, statistics shows that creative people with higher IQ are more likely to suffer from bipolar disorder and mood swings. Most studies done on this subject were small but all show similar results nonetheless.
One study among the students in Swedish schools found that those with higher grades were more likely to show signs of bipolar disorder. However, the study also demonstrated that students with the lowest grades were twice more likely to show signs of bipolar disorder compared to the average students. Interestingly, a New Zealand study showed similar associations between low IQ and psychiatric disorders.
Another study published in The Archive of General Psychiatry showed that people with higher IQ were less likely to suffer from post-traumatic stress disorder. This study has considered socioeconomic variables, as discussed earlier.
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Source material from Brain Blogger