The switch process in manic-depressive illness. Circadian variation in time of switch and sleep and manic ratings before and after switch.

Research data collected on 75 Bipolar I patients, hospitalized at the NIMH between 1963 and 1975, were reviewed to identify "switches" into and out of mania. There were 27 "slow" switches (i.e. occurring over a period of 2--6 days) in 14 patients and 89 "rapid" switches (i.e. occurring in 24 hours or less) in 35 patients. No patient showed both "rapid" and "slow" switches during his hospitalization. Among the 89 rapid switches, 52 switches were into mania and 37 were out of mania. Rapid switches into and out of mania occurred significantly more often in the morning (7 a.m. to 3 p.m.) than at night (11 p.m. to 7 a.m.) or in the evening (3 p.m. to 11 p.m.). Estimated average sleep time on the night prior to switch into mania showed a significant drop as compared to sleep time on the second, third and fourth nights prior to switch. Patients who switched into mania at night were rated as significantly more manic during the 4 days following the switch than patients who switched in the morning or evening. Patients who switched into mania at night and evening were rated as sleeping significantly less during the 4 days following the switch than patients who switched in the morning.