Research Summaries: Childhood IQ and risk of bipolar disorder in adulthood: prospective birth cohort study
Today’s research summary focuses on an article [pdf] that throws some light on the oft debated question of the association between intelligence, creativity and mental illness.
- It has been hypothesized that various mental illnesses like Bipolar disorder, Schizophrenia etc persist in the gene pool because they are associated with some positive mechanisms that also confer survival or mating benefits, either to the patients or their close relatives. One such mechanism is thought to be apophenia (ability to see patterns, sometimes when there are none:-) ) , which is related to divergent thinking, imagination and creativity; another such mechanism is thought to be intelligence or the ability to solve complex adaptive problems flexibly.
- One method to settle the debate is correlational in nature. Sweden maintains rich and exhaustive data about its citizens. Mining data form the Swedish population registries, it was found that bipolar patients, as well as their relatives, were more likely to be in creative professions; and that bipolar traits may be associated with leadership qualities.
- Another method is to look at twins, one of which has the bipolar disorder, while the other hasn’t; and it was found that the other twin had high scores on sociability and verbal fluency; hinting that these may be linked to the bipolar proband.
- Yet another method is to look at longitudinal studies like the Dunedin studies, which track a child cohort since birth or early age and track them over time. The Dunedin studies found that low childhood IQ was associated with Schizophrenia spectrum disorder, depression an anxiety in adulthood; but high IQ was associated with mania in adulthood.
- The authors of this study used a longitudinal study design, analyzing the results of ALSPAC, a large UK birth cohort. This cohort consist of about 15,500 participation, but after all the dropout etc only about 2000 subjects results were part of the study results.
- This study focused on association of childhood IQ (which is an imperfect measure of true intelligence) with propensity for bipolar disorder in young adulthood. This study did not look at creativity and did not look at actual occurrence of bipolar disorder, thus all the results should not be extrapolated wildly.
- Childhood IQ at age 8 was measured using WISC-III and separate verbal and performance IQ as well as Full IQ scores were used in analysis. Propensity towards bipolar was measured using HCL-32 (hypo-mania checklist) which consist of 32 yes/no answers to statements like ‘I am more easily distracted’ when in a state of ‘high’ not associated with drug use. Only 28 items from this checklist were used. This was administered at ages 22-23 years.
- Childhood IQ was indeed associated with higher scores on HCL-32. The scores on HCL-32 were converted into percentile scores. Those subjects, who were in the lowest decile of HCL-32, or alternately had the lowest risk for later bipolar, had IQ scores that were 10 points on average lower than those subjects who were in the highest decile of HCL32 (had the highest bipolar risk).
- The IQ scores were also made categorical. Looking at data from another way, those who had the lowest verbal IQ scores (were in the ‘extremely low’ of VIQ) had on an average 7.1 points less score on HCL-32 than the ‘average’ VIQ group. The ‘ Very superior’ VIA group had scores 1.83 points higher than ‘average’ IQ group.
- As the age at which, HCL-32 was administered, not many people have the first manic/ depressive episode; so it might be capturing risk towards bipolar rather than actual incidence. Verbal fluency seems a more stronger predictor of bipolar risk than intelligence per se.
- As per my views, Bipolar pro-band may have more to do with creativity than intelligence and if future studies could operationalise and measure childhood creativity and look at later risk or occurrence of bipolar disorder, than that will settle the debate to an extent. Also important to remember that intelligence and creativity though correlated are different, with one perhaps requiring a threshold of intelligence to be creative.
- Lastly, if you are intelligent or creative, don’t fear, the risks seem to be too small and other factors like stress play a much more important role in triggering an illness. And even when triggered, it can be managed well!
If you liked the study and want to dig deeper, the full text article [pdf] is online.
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