Recurrent unipolar depressions with a 48-hour cycle: report of a case.

Since 1804 there have been twelve case reports of patients with mood disorders showing a regular periodicity of 48 hours, eight bipolar and four unipolar. This paper describes an additional patient, a 57-year-old man with a 48-hour unipolar cycle. Although his 24-hour serum cortisol pattern was abnormal, there were few clear-cut biological abnormalities. Possible mechanisms are discussed, and comparisons made with previous reports of similar patients.