Seasonal affective disorder presenting as chronic fatigue syndrome

Although operational criteria have been recently proposed to better define chronic fatigue syndrome (CFS), it remains a controversial diagnosis. There are many overlapping symptoms between CFS and major depression. The author presents two patients with seasonal affective disorder, who responded to phototherapy and had previously been diagnosed as CFS. Because of the consequences of treatment, seasonal and non seasonal depression need to be ruled out in patients with chronic fatigue symptoms.