Researchers at Oregon Health & Science University (OHSU) have found that melatonin, a naturally occurring brain substance, can relieve the doldrums of winter depression, also known as seasonal affective disorder, or SAD.
The study, published in the Proceedings of the National Academy of Science, was led by Alfred Lewy, MD, PhD. Lewy and his colleagues in the OHSU Sleep and Mood Disorders Lab set out to test the hypothesis that circadian physiological rhythms become misaligned with the sleep/wake cycle during the short days of winter, causing some people to become depressed.
The treatment of choice for most SAD patients is bright light exposure, which causes phase advances when scheduled in the morning. Because patients know when they are exposed to bright light, however, there is a considerable placebo response associated with it. Melatonin can also cause phase advances, but it has to be taken in the afternoon. The Lewy team used afternoon melatonin to test if it was more antidepressant than melatonin taken in the morning, which causes phase delays.
The researchers randomly assigned 68 SAD patients to one of three treatment groups, taking placebo capsules or melatonin in the morning or afternoon for three weeks. After 4 years of study, they concluded that, similar to persistent jet lag, circadian misalignment is a major part of SAD.
