Familial transmission of seasonal changes in sleep and eating function in the general population

Both genetic and environmental factors may be involved in the development of the increased sleep and appetite/body weight during winter, which are observed in seasonal affective disorder (SAD) as well as in normal variants of behavior in the general population. Decreases of these psychosomatic functions are also observed during summer, although the change may be less apparent than the winter changes. We studied familial correlation of these seasonal changes in 129 small Japanese families of the general population, using the Seasonality Pattern Assessment Questionnaire (SPAQ). No association was observed between the child and biological parents in the changes of sleep length or appetite/body weight during winter or summer. In contrast, significant spouse correlations were found in the changes of sleep and eating function during winter as well as during summer. This may indicate a role of shared environmental factors in the development of the seasonal patterns. The present results are preliminary and further studies are recommended.