Prevalence of bipolar symptoms in epilepsy vs other chronic health disorders.

OBJECTIVE: To estimate the comparative prevalence of bipolar symptoms in respondents with epilepsy vs other chronic medical conditions.

METHODS: The Mood Disorder Questionnaire (MDQ), a validated screening instrument for bipolar I and II symptoms, in conjunction with questions about current health problems, was sent to a sample of 127,800 people selected to represent the US adult population on selected demographic variables. A total of 85,358 subjects (66.8%) aged 18 or older returned the survey and had usable data. Subjects who identified themselves as having epilepsy were compared to those with migraine, asthma, diabetes mellitus, or a healthy comparison group with regard to relative lifetime prevalence rates of bipolar symptoms and past clinical diagnoses of an affective disorder.

RESULTS: Bipolar symptoms, evident in 12.2% of epilepsy patients, were 1.6 to 2.2 times more common in subjects with epilepsy than with migraine, asthma, or diabetes mellitus, and 6.6 times more likely to occur than in the healthy comparison group. A total of 49.7% of patients with epilepsy who screened positive for bipolar symptoms were diagnosed with bipolar disorder by a physician, nearly twice the rate seen in other disorders. However, 26.3% of MDQ positive epilepsy subjects carried a diagnosis of unipolar depression, and 25.8% had neither a uni- nor bipolar depression diagnosis.

CONCLUSION: Bipolar symptoms occurred in 12% of community-based epilepsy patients, and at a rate higher than in other medical disorders. One quarter were unrecognized.