The timing of light therapy and response assessment in winter depression.

Since Rosenthal et al published their first study about the effects of light treatment on mood in patients suffering from winter depression, many research centres have become interested in the study and treatment of seasonal affective disorders (SAD), one of them being the department of Biological Psychiatry in Groningen. In 1987, we started the first experiments under the inspiring direction of Prof. Rudi van den Hoofdakker and hundreds of patients have participated in various investigations ever since.