The serious disorders of mood such as bipolar disorder may be a result of more adaptive traits such as intelligence, creativity and verbal proficiency, said the research published in the British Journal of Psychiatry.
Scientists at the Universities of Glasgow, Bristol, Cardiff and Texas looked at data from the 'Children of the 90s' birth cohort, officially called the Avon Longitudinal Study of Parents and Children (ALSPAC), and found that higher childhood IQ could indicate greater risk of bipolar disorder in adulthood.
"We are not saying that high childhood IQ is a clear-cut risk factor for bipolar disorder but rather that there is likely to be a shared biology between intelligence and bipolar disorder which needs to be understood more fully," Smith said.
The researchers examined data from ALSPAC to look for an association between measures of childhood IQ at age eight and lifetime manic features assessed at 22-23 years.
The final results, which combined data from 1,881 individuals, showed a positive association between the two.
Individuals who scored in the top 10 per cent of manic features had a mean childhood IQ which was almost 10 points higher than those scoring in the lowest 10 per cent of manic features. The association between IQ and manic features appeared to be strongest for verbal IQ (VIQ).
"Our finding has implications for understanding how liability to bipolar disorder may have been selected through generations. One possibility is that serious disorders of mood such as bipolar disorder are the price that human beings have had to pay for more adaptive traits such as intelligence, creativity and verbal proficiency," Smith said.
"The results of this study are very interesting. Studies of this kind are also important in the battle to tackle stigma," said Alison Cairns, Chief Executive of Bipolar Scotland.
