A high childhood IQ is linked to an increased risk of bipolar disorder in adulthood, according to new research published in the British Journal of Psychiatry.
Scientists from the Universities of Glasgow, Bristol, Cardiff and Texas examined data from a large birth cohort, the Avon Longitudinal Study of Parents and Children (ALSPAC), to identify the IQ of 1881 children at the age of eight. These same individuals were then tested for manic traits at the age of 22 or 23.
Each person gave statements that provided a score out of 100 relating to how many manic traits they had previously experienced. The test also included questions from a checklist often used to diagnose bipolar disorder. It was found that individuals who scored in the top 10 percent of manic features had a childhood IQ almost 10 points higher than those who scored in the bottom 10 percent. This association appeared to be strongest for those with a high verbal IQ.
Lead author Professor Daniel Smith from the University of Glasgow said: '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,' he added.
Professor Smith emphasised that having a high IQ is only an advantage. He told the Guardian: 'A high IQ is not a clear-cut risk factor for bipolar, but perhaps the genes that confer intelligence can get expressed as illness in the context of other risk factors, such as exposure to maternal influenza in the womb or childhood sexual abuse.'
Previous studies have also found a link between 'creativity' and the risk of schizophrenia and bipolar disorder (see BioNews 806), as well as a possible association between autism-related genes with higher intelligence (see BioNews 794).
One in every 100 people in the UK is affected by bipolar disorder, which causes extreme moods swings with sufferers experiencing switching periods or episodes of depression and mania.
Chief executive of Bipolar UK, Suzanne Hudson, said: 'Given the rise in requests for support from parents and families of children to Bipolar UK, research that helps identify young people more at risk of developing bipolar disorder is vitally important'.