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Prior ADHD, anxiety diagnoses may predict bipolar disorder

Individuals in Denmark who had prior diagnoses of both ADHD and anxiety were 30 times more likely to develop bipolar disorder than those with no prior ADHD or anxiety, according to research findings published in The British Journal of Psychiatry.

“Prior evidence on whether ADHD and anxiety alone or in combination predict bipolar disorder may be inconsistent because it is limited to familial high-risk samples of moderate size, where the number of prospectively ascertained onsets may not be sufficient to conduct tests with adequate statistical power and existing genetic diathesis may confound the apparent associations,” Sandra M. Meier, PhD, of the Psychosis Research Unit, Aarhus University Hospital, and The Lundbeck Foundation Initiative for Integrative Psychiatric Research in Denmark, and colleagues wrote.

Researchers examined the prospective relationship between bipolar disorder, ADHD and any anxiety disorders in a birth cohort of more than 2 million people born in Denmark between 1955 and 1991. The participants were followed from age 16 years or from January 1995 to adult-onset bipolar disorder or until end of 2012 using data from national Danish registries. In their analysis, Meier and colleagues calculated incidence rates per 10,000 person-years and examined the effects of prior ADHD and/or anxiety diagnoses on the risk for bipolar disorder using survival models.

Out of 37,394,865 person-years follow-up, 9,250 people experienced bipolar disorder onset. Overall, prior diagnosis of ADHD increased the incidence of bipolar disorder 11.29-fold (95% CI, 9.72-13.03) compared with those without ADHD, and prior diagnosis of anxiety disorder increased the incidence of bipolar disorder 12.05-fold (95% CI, 11.3-12.83; P < .001) compared with those without prior anxiety. Those with combination ADHD and anxiety disorders had a 30-fold increased risk for bipolar disorder onset (95% CI, 21.66-41.4) than those with no previous ADHD or anxiety.

The incidence rate of bipolar disorder in adults with no previous ADHD or anxiety disorder was 2.17 (95% CI, 2.12–2.19), whereas those with only prior ADHD diagnosis had an incidence rate of 23.86 (95% CI, 19.98–27.75) and those with only prior anxiety diagnosis had a rate of 26.05 (95% CI, 24.47–27.62). However, in individuals with both ADHD and anxiety, the incidence rate of bipolar disorder was 66.16 (95% CI 44.83–87.47).

“Quantification of risk for bipolar disorder in each subgroup is essential to inform public health and clinical decisions,” Meier and colleagues wrote. “The 30-fold increase in risk of bipolar disorder among those with a history of both ADHD and anxiety may indicate the need for targeted early pre-emptive interventions.” – by Savannah Demko

Disclosure: The authors report no relevant financial disclosures.