Bright fluorescent Vitalite (TM) (2000-2500 lux) was presented to 2 subjects with Seasonal Affective Disorder (SAD) and 3 normal controls 2 hours prior to bedtime for one week. Oral temperature and heart rate were measured during this time in the two groups and compared to 7 days of baseline measurements made the week before where the subjects sat quietly in dim light and monitored their temperature and pulse. Bright evening light prevented the fall in oral temperature in both SAD subjects and one normal control. Bright light also prevented the normal fall of heart rates in SAD subjects but not in normal controls. 2. Bright evening lights also produced a significant delay in sleep onset that was cumulative over the seven days in SAD subjects but was also present but less pronounced in 2 normal controls. 3. Evening light produced "activation" that was generally pleasant but produced significant irritability in one SAD subject.
