Ybe Meesters,1 Marijke CM Gordijn,2,3 1University Center for Psychiatry, University Medical Center Groningen, 2Department of Chronobiology, GeLifes, University of Groningen, Groningen, the Netherlands; 3Chrono@Work B.V., Groningen, the Netherlands Abstract: Seasonal affective disorder (SAD), winter type, is a seasonal pattern of recurrent major depressive episodes most commonly occurring in autumn or winter and remitting in spring/summer. The syndrome has been well-known for more than three decades, with light treatment being the treatment of first choice. In this paper, an overview is presented of the present insights in SAD. Description of the syndrome, etiology, and treatment options are mentioned. Apart from light treatment, medication and psychotherapy are other treatment options. The predictable, repetitive nature of the syndrome makes it possible to discuss preventive treatment options. Furthermore, critical views on the concept of SAD as a distinct diagnosis are discussed. Keywords: seasonal affective disorder, review, light treatment, medication, psychotherapy, prevention