Critical approach to the concept of seasonal depression and phototherapy

Since Rosenthal's princeps study in 1984, phototherapy represents a novel t herapeutic tool which is inseparably linked to seasonal affective disorder (SAD), its principal indication. The authors describe certain methodologica l causes of disparity in SAD study results, address the major question of p lacebo effect, and discuss the descriptive, predictive and therapeutic vali dity of the SAD concept, the latter being currently the,most significant. Seasonal rhythmicity ir? mood disorders should be demonstrated scientifical ly before invoking biological factors.