SLEEP ELECTROENCEPHALOGRAM IN SEASONAL AFFECTIVE-DISORDER AND IN CONTROL WOMEN - EFFECTS OF MIDDAY LIGHT TREATMENT AND SLEEP-DEPRIVATION

The role of sleep regulation in Seasonal Affective Disorder (SAD) was studied in II female SAD patients and eight controls in winter before and after light treatment (LT, 6000 lux 10-14h, 5 days). The sleep ele ctroencephalogram (EEG) was recorded at baseline and after the total s leep deprivation (TSD) of a 40-h constant routine. The well-known effe cts of TSD on sleep parameters and on EEG power spectra were replicate d, indicating normal homeostatic sleep regulation in SAD. Sleep improv ed after LT in both groups. Since the condition following LT was the s econd session these improvements may be an order effect and/or an effe ct of LT itself. After LT, sleep EEG spectra of SAD patients, but not of controls, showed modifications resembling those of recovery sleep. Since only SAD patients curtailed their sleep while remitting during t he LT period, these EEG modifications can be explained by normal sleep regulation alone. We conclude that the robust antidepressant effect o f LT in SAD is unlikely to be mediated by changes in sleep, and that s leep regulatory mechanisms are not a crucial factor in the pathogenesi s of winter depression.