By Eleanor McDermid, Senior medwireNews Reporter
Children with attention deficit/hyperactivity disorder (ADHD) who also have conduct disorder/oppositional defiant disorder (CD/ODD) or anxiety disorder are at an increased risk of developing bipolar disorder, research shows.
The strong effect of these comorbidities “provides an impetus for prioritizing prevention and preemptive strategies to reduce their hazardous influence on the onset and progression of bipolar disorder”, say Jeanette Jerrell (University of South Carolina School of Medicine, Columbia, USA) and study co-authors.
But it remains to be seen whether such strategies can actually reduce progression to bipolar disorder, they add.
CD/ODD had the strongest effect overall, increasing the likelihood of bipolar disorder 4.01-fold after accounting for the duration of exposure to pharmacotherapies. Furthermore, the disorder was very common, occurring in 40% of the 22,797 ADHD patients in the study, who were identified in a medical claims database.
Anxiety disorder was less common, occurring in 15% of the patients, but was nonetheless associated with a significant 2.39-fold increased likelihood of bipolar disorder.
ADHD was diagnosed at an average age of 7.8 years, followed by CD/ODD and anxiety disorder at an average of 10.3 and 11.7 years, respectively. Bipolar disorder, which occurred in 7% of the cohort, was diagnosed at an average age of 12.2 years.
The associations between these psychiatric conditions imply “an underlying biological etiology that requires further investigation”, say the researchers.
Jerrell et al note that “a major challenge for improving outcomes is the large lag time between symptom onset, first correct diagnosis, and appropriate treatment.” They suggest that better characterisation and understanding of the prodromal period could facilitate early intervention.
Substance abuse, although associated with a 1.88-fold increased likelihood of a bipolar disorder diagnosis, usually developed after the diagnosis, at an average age of 15.9 years. “Therefore, it may represent a secondary condition, perhaps developing due to inadequate control of the multiple symptom constellations present in these complex cases”, the team writes in The Journal of Clinical Psychiatry.
The children were given a variety of medications for their ADHD, and the length of treatment with some medications (methylphenidate, mixed amphetamine salts or atomoxetine) was associated with a significantly increased risk of a bipolar diagnosis, but only by 1% per month of treatment, “so their observable clinical impact may be minimal”, say the researchers.
Use of antidepressants was associated with about a twofold increased risk of a bipolar disorder diagnosis, with the relative risk increase being broadly similar across the different medications used.
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