High Verbal IQ in Childhood Linked to More Manic Traits in Adulthood

Researchers track over two decades of data from a major British birth cohort

Children who score higher on IQ tests—especially on verbal skills—show more manic-like traits in their early 20s than peers with average scores, according to a long-running British study.

The link suggests intellectual ability could be a marker for later bipolar-spectrum features, researchers say.

The study, led by scientists at the University of Glasgow analyzed data from the Avon Longitudinal Study of Parents and Children, a well-known birth cohort that has followed thousands of families since the early 1990s.

The team compared IQ measured at age 8 with lifetime manic features self-reported at ages 22–23, aiming to clarify how early cognitive profiles relate to later mood symptoms.

Researchers found a small but statistically significant association: children with higher full-scale IQs reported more manic features in young adulthood, with the strongest link seen for verbal IQ.

On average, those in the highest decile of manic-feature scores had childhood IQs about 10 points higher than those in the lowest decile (110.1 vs. 100.7). The correlation between age-8 IQ and later manic features was 0.159. Analyses accounted for factors such as sex, ethnicity, maternal education, maternal social class, maternal age, and maternal history of depression.

The team used the Hypomania Checklist-32, a validated screening tool, to capture lifetime manic traits rather than relying on clinical diagnoses alone.

That “dimensional” approach, they argue, increases statistical power and avoids arbitrary cutoffs for defining hypomania. Childhood IQ came from a short form of the Wechsler Intelligence Scale for Children administered in clinic visits at age 8.

The findings build on earlier population studies hinting at ties among intelligence, creativity, and bipolar disorder. Prior work in Sweden, for example, has reported that individuals with bipolar disorder and their unaffected siblings are more often employed in creative fields, and that high verbal or technical ability may be linked to bipolar disorder.

The authors caution that the association does not mean high IQ causes bipolar disorder, nor that most bright children will develop a mood illness. Bipolar disorder is influenced by many genetic and environmental factors, and the observed relationship was modest.

Still, they say, verbal proficiency may be a signal—an underlying trait—that co-travels with liability to mania. That could help explain why bipolar disorder persists across generations and may guide future genetic and developmental research at the intersection of intelligence and mood.

Source: Smith DJ, Anderson J, Zammit S, et al. “Childhood IQ and risk of bipolar disorder in adulthood: prospective birth cohort study,” BJPsych Open, published Aug. 20, 2015.

Note from a person living with bipolar I: When I was 7-years-old my first IQ test in school scored me higher than average by more than 10 points. My anecdotal experience fits with the study above.

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