Morning or night-time melatonin is ineffective in seasonal affective disorder.

Melatonin, at the same doses used to treat circadian-rhythm related sleep disturbances, had no effect on the depressive symptoms in seasonal affective disorder (SAD) patients, whether given early (7 a.m.) or late (11 p.m.) for a week. Slight improvements in sleep were seen with nighttime administration. The circadian rhythmicity of urinary 6-sulphatoxymelatonin was not modified in any way. Melatonin at this dosage (5 mg/day) or at these two times is therefore not a potential alternative treatment for SAD; light remains the therapy of choice.