Spontaneous eye blink rate in winter seasonal affective disorder

Abstract

We investigated spontaneous eye-blink rates in 19 drug-free patients with winter seasonal affective disorder (SAD) and 18 normal control subjects. At baseline, there were no significant differences between the two groups (mean ±SD blink rate: 15/minute± 8 vs. 15/minute± 7). Light therapy (10,000lux: 1 hour each morning for 1 week) produced no significant change in mean (± SD) blink rates either in 10 SAD patients (13/minute ± 8 vs. 10/minute ± 7) or in 12 normal control subjects (15/minute ± 6 vs. 14/minute ± 6). A post hoc exploratory analysis of the effect of light therapy on premenopausal female subjects (5 patients and 9 control subjects) showed a significant decrease in mean (± SD) blink rate in the patients after treatment (17 ± 6 vs. 12 ± 8 compared with 15 ± 7 vs. 16 ± 5). These results do not support the idea that an elevated blink rate may be a general biological marker in SAD, but they suggest a possible link between light treatment and mechanisms that regulate blink rate in premenopausal SAD patients.