Patients with seasonal affective disorder have lower odor detection thresholds than control subjects

Background: Behavioral changes in patients with seasonal affective disorder resemble seasonal changes in photoperiodic animals. Because the olfactory system has a modulatory role in seasonal photoperiodic responses in certain species, we hypothesized that olfactory function may differ between patients with seasonal affective disorder and healthy control subjects. Methods: Fourteen patients who had winter seasonal affective disorder and 16 healthy volunteers were studied once in winter and once in the subsequent summer. We administered a phenyl ethyl alcohol detection threshold test to each side of the nose in a counterbalanced order, with the nostril contralateral to the tested site occluded. Patient and control data were compared using a 4-way repeated measure analysis of covariance (with group and gender as between-subjects factors, season and side-of-the-nose as within-subjects factors, and age as a covariate). Results: The patients exhibited lower thresholds than did the controls (F_1.25=9.2; P=.006). There was no main effect of season. Conclusion: In humans, marked seasonal behavioral rhythms with recurrent winter depression may be associated with a more acute sense of smell.