Comorbidity of delusional disorder with bipolar disorder: report of four cases.

BACKGROUND Although it is accepted that patients with delusional disorder can show co-existing depression, comorbidity with bipolar disorder is not a recognised feature. METHOD Case report of patients who showed both delusional disorder and mania or hypomania. The patients were examined using lifetime structured psychiatric interview where possible. RESULTS Four patients are described who met criteria for delusional disorder, with durations ranging from 2 to 15 years, and also experienced one or more episodes of mania or hypomania. LIMITATIONS Case reports cannot quantify a clinical association. CONCLUSIONS These cases suggest that there is an association between delusional disorder and affective disorder which goes beyond the occurrence of depressive symptoms in the disorder.