Cluster headache and bipolar disorders: Phenotypical overlap and comorbidity

Background and objectives Cluster headache (CH) and bipolar disorder (BD) are cyclic disorders with shared clinical aspects, e.g. disturbed sleep patterns, response to lithium and a tendency to use illicit drugs. We investigated comorbidity of BD in patients with CH, familial aggregation of BD, circadian aspects and use of illicit drugs. Methods 310 Patients from the Leiden University Cluster headache neuro-Analysis program (LUCA) were screened cross-sectionally for BD online, using the Mood Disturbance Questionnaire (MDQ-NL) and Altman Self Rating Scale (ASRM-NL) and, if indicated, further evaluated with the Mini international neuropsychiatric interview (MINI). Circadian aspects were analyzed using the Circadian Type Inventory (CTI) and the Munich Chronotype Questionnaire (MCTQ). Results The life-time prevalence of BD in patients suffering from CH was 6.5% (20/310; 95% CI: 4.0-9.8%). Patients with comorbid BD (CH+BD) were more likely to have family members with BD (standardized OR= 1.50, 95% CI=1.15;1.95, p=0.003) and were more likely to suffer from chronic CH (OR=3.05 95% CI=1.18;7.87, p=0.02) after adjustment for age and sex. They also more often used illicit drugs, compared to patients with only CH. Circadian type and chronotype did not differ between the two groups after adjustment for confounders. Conclusion It is important to screen for BD when treating patients with CH, because BD is more prevalent than expected in this population.