The circadian rhythm of temperature during light treatment for winter depression.

Circadian rhythm abnormalities have been implicated in winter seasonal affective disorder. We examined the circadian temperature rhythm of 22 patients with winter depression and 10 normal controls who had participated in various high-intensity light treatment experiments. We did not find abnormalities in the baseline phase or amplitude of the temperature rhythm in patients compared to controls. Nor did we find abnormalities in the phase-shifting response to morning light. There was some evidence that the "phase-delayed" half of the patients responded poorly to phase advances produced by morning light, whereas the "phase-advanced" half of the patients responded poorly when their rhythms delayed. However, the antidepressant responses during the best week (week of lowest depression score) were unrelated to temperature rhythm phase shifts. In general, there was not strong support for a relationship between circadian rhythms changes and antidepressant response.