Over the Counter Treatment for Seasonal Affective Disorder
The short story: Low daily doses of liquid melatonin taken every day for 4 weeks once SAD has set in, can lift the mood. A low dose of melatonin - .3 mg - can be obtained by using small amounts of liquid melatonin. The time of day it is taken is important. For most people it is in the afternoon. For some (30%) it should be taken in the morning. (Per research (2) cited below.)
Melatonin is available over the counter, but one should consult a doctor regarding usage.
A running theory of the cause of seasonal affective disorder (SAD) or winter depression, is that a person's circadian rhythms are out of sync. NIHM defines this: "A person's rhythms are synchronized when the interval between the time the pineal gland begins secreting melatonin and the middle of sleep is about 6 hours. (1)" There are a number of therapies aimed at correcting the problem including lights, exercise, anti-depressants and melatonin. (See the Wikipedia entry.)
The synchronization can be off in two ways: - a longer-than or a shorter-than 6 hour interval. A study by Lewy, et al (2), showed that subjects who took low dosages of melatonin every day for 4 weeks found an improvement in mood. The dosage was as follows: for those who's interval is less than 6 hours, .3 mg in the afternoon. For those with a longer than 6 hour interval, .3 mg in the morning. If you have to guess which you are, the odds from the study favor the short interval (71% to 29%). The study gave 2 small doses adding up to .3 mg in 2 hours.
Melatonin is available over the counter, but generally in high dose formulations. The study used capsule formulation. There are liquid forms of melatonin available in some health food stores. (Again, I found Natrol 1 mg, and adjusted the amount.)
Both articles cited are available on line.
1. April 2006 article from the National Institute of Mental Health, "Properly Timed Light, Melatonin Lift Winter Depression by Syncing Rhythms".
2. Lewy AJ, Lefler BJ, Emens JS, Bauer VK. The circadian basis of winter depression. Proc Natl Acad Sci U S A. 2006 Apr 28.