Background: Anecdotal and biographical reports suggest that bipolar disorder may be associated with high IQ or creativity, but evidence for any such connection is weak.
Aims: To investigate possible associations between scholastic achievement [GPA] and later bipolar disorder, using prospective data, in a whole-population cohort study.
Method: Using individual school grades from all individuals finishing compulsory schooling in Sweden 1988–9199727ya, we tested associations between scholastic achievement at age 15–16 and hospital admission for psychosis ages 17–31, adjusting for potential confounders.
Results: Individuals with excellent school performance had a nearly 4× increased risk of later bipolar disorder compared with those with average grades (hazard ratio HR = 3.79, 95% CI 2.11–6.82). This association appeared to be confined to males.
Students with the poorest grades were also at moderately increased risk of bipolar disorder (HR = 1.86, 95% CI 1.06–3.28).
Conclusion: These findings provide support for the hypothesis that exceptional intellectual ability is associated with bipolar disorder.
…Table 2 shows the association between school performance and risk of bipolar disorder by z-score category. Individuals at both the low and high ends of the school grades distribution had a substantially higher risk for bipolar disorder. Those in the highest grade category, with grades of two or more standard deviations above the mean, were nearly 4× more likely to develop bipolar disorder than those with average scores, whereas those in the lowest grade category were around twice as likely.
The association was slightly attenuated in the fully adjusted model, controlling for parental education, socioeconomic group and other potential confounders, but the associations with both high and low grades remained. The addition of confounders to the model had small, but opposite, effects on the associations between high and low scores and bipolar disorder. The association between high school performance and bipolar disorder was attenuated, suggesting that some confounding may have been present. However, the association between low school performance and bipolar disorder was accentuated, suggesting negative confounding (unmasking of a true effect). Further analyses (not shown) demonstrate that most of this pattern of positive and negative confounding was attributable to parental education. Thus, the association between high school performance and bipolar disorder may be partly confounded by high parental education, whereas the relationship between low school performance and bipolar disorder may have been masked by the fact that individuals with bipolar disorder had better-educated parents, which had ‘pulled up’ their scores.
Figure 1 shows the incidence rate of bipolar disorder for individuals in each performance category of grade-point average. For comparison, incidence rates of schizophrenia in the same sample (reported separately in Mac et al 2008) are shown alongside. The contrast with schizophrenia is most marked at higher levels of school achievement, which are associated with increased risk of bipolar disorder but decreased risk of schizophrenia.
…Comparison with previous findings: Previous cohort studies investigating premorbid cognitive function in bipolar disorder have shown either performance within the normal range ( et al 2002, et al 2004) or deficits in specific domains such as visuospatial reasoning ( et al 2005).
Some previous cohort studies have, however, provided tentative evidence of superior premorbid educational or cognitive performance in bipolar disorder. In a population-based Finnish study, Aro and colleagues found higher admission rates for bipolar disorder in people who had completed >12 years of education, particularly in males, whereas the reverse was true for other psychotic and affective disorders. In the Dunedin Cohort, Cannon and colleagues ( et al 2002) examined prospectively collected data on premorbid cognitive and neuromotor development in ~1,000 children. Children who would develop mania in adulthood outperformed controls on motor performance, controlling for gender and socioeconomic status. Very recently, the same researchers showed ( et al 2008) that those children who went on to develop mania also had statistically-significantly higher IQs than the remainder of the cohort, but the authors acknowledged that the sample was small, with only 8 children going on to develop mania, and they called for replications in a larger sample.
Gender differences: The association between high scores and risk for bipolar disorder seems to be confined to males, although the formal test for interaction between school marks and gender was not statistically-significant. Replication will be required before we can draw any firm conclusions as to whether the association is truly stronger in males.
However, it is notable that the great majority of the eminent creative individuals with probable bipolar disorder described in the biographical studies of Jamison and others were male. [2010, Manic depression and creativity; 1996, Touched with fire; 2001, Strong imagination: Madness, creativity and human nature; 1989; 1996; 2003; 1987]