In seasonal affective disorder (SAD) is associated with winter depression Typically, these individuals not only feel depressed they also feel tried, slow down, and generally oversleep, overeat, and crave carbohydrates in the winter. In the summer, these same patients feel very good and maybe even are elated, active, and energetic.
Although many variables may be responsible for SAD, insufficient light exposure is the most logical explanation. Many mammals exhibit seasonal variations in activity level, sleep patterns, and appetite and are extremely sensitive to changes in day length. The antidepressant effects of full-spectrum light therapy have been demonstrated in well-monitored, controlled studies in SAD. The antidepressant effect of light therapy is probably due to the restoration of proper melatonin synthesis and secretion by the pineal gland, leading to reestablishment of the proper circadian rhythm. Full-spectrum white light (10,000 lux) is prescribed for at least 30 minutes every day in the morning. Or, better yet, use full-spectrum lighting throughout the indoor environment.