Seasonal changes in mood and behavior: a cluster analytic approach.

We report on the cluster analysis of 416 subjects from Montgomery County, Maryland, USA, who responded to lay interviewers using a telephone version of the Seasonal Pattern Assessment Questionnaire (SPAQ). Eight clusters are described, the smallest of which is consistent with a pattern comparable to that seen in patients with winter seasonal affective disorder (SAD). A larger group of individuals seems to demonstrate patterns equivalent to that of subsyndromal winter SAD patients. Furthermore, it was apparent that a large percentage of the study group seems to be affected to some degree by the characteristics of the seasons. It was observed, perhaps for the first time, that feeling worse when there is a high pollen count appears to be associated with the symptom pattern seen in winter SAD patients. There is also evidence for the existence of a group of summer subsyndromal SAD subjects.