Seasonal variations in mood and behavior in the general population: a factor-analytic approach.

In a mailed survey conducted at four centers--Nashua, NH; New York, NY; Washington, DC; and Sarasota, FL--1,671 respondents provided information on monthly variations in 10 behavioral categories representing extremes in the areas of mood, socializing, appetite, weight gain/loss, and sleep length. A 10-factor solution revealed the following factors: (1) a winter weight gain factor; (2) a winter depression factor; (3) a winter hypersomnia factor; (4) a summer weight gain factor; (5) a summer hypersomnia factor; (6) a summer depression factor; (7) a winter socializing factor; (8) a winter weight loss factor; (9) a fall depression factor; and (10) a possibly mixed factor. Factors consistent with winter seasonal affective disorder were positively correlated with latitude, while those consistent with summer seasonal affective disorder were negatively correlated with latitude.