The effects of amitriptyline and lithium on a patient with 48-hour recurrent depressions.

A 61-year-old man with a 5-year history of 48-hour mood swing cycles--1 day depressed, 1-day euthymic--was treated with medications in a double blind trial. Placebo had no effect on his cycles, amitriptyline lessened the amplitude of depression on "bad days" but did not effect the 48-hour periodicity, whereas lithium carbonate therapy terminated both affective symptoms and the cycle itself. After several months on lithium, the patient discontinued the drug, but neither symptoms nor cycles returned. Forty-eight-hour affective cycles are unusual, and this patient's response to lithium is particularly striking.