Epidemiological studies and studies of clinical populations suggest that there are primarily two opposite patterns of seasonally recurring depressions: summer depression and winter depression.
In addition, there is preliminary evidence that the two seasonal types of depression may have opposite types of vegetative symptoms.
In the present study, we prospectively monitored symptoms of depression in 30 patients with recurrent summer depression and 30 sex-matched patients with recurrent winter depression and compared the symptom profiles of the two groups.
Consistent with predictions based on the earlier reports, we found that winter depressives were more likely to have atypical vegetative symptoms, with increased appetite, carbohydrate craving, weight gain and hypersomnia [sleeping more], and that summer depressives were more likely to have endogenous vegetative symptoms, with decreased appetite and insomnia.
A cluster analysis performed on the patients' symptom profiles without reference to season of occurrence of their episodes separated 78% of the summer depressives and winter depressives from each other on the basis of their symptoms (chi 2 = 19.29, P less than 0.001).
Source: Journal of Affective Disorders, 1991 Dec;23(4):173-83. PMID: 1791262 by Wehr TA, Giesen HA, Schulz PM, Anderson JL, Joseph-Vanderpool JR, Kelly K, Kasper S, Rosenthal NE. Clinical Psychobiology Branch, National Institutes of Mental Health, Bethesda, Maryland, USA.