What are the key diagnostic criteria for Seasonal Affective Disorder (SAD) in adults?

The key diagnostic criteria for Seasonal Affective Disorder (SAD) in adults include the presence of a recurrent major depressive episode that occurs with a seasonal pattern, typically beginning in autumn or winter and remitting in spring or summer. This seasonal pattern must have been observed for at least two consecutive years without non-seasonal depressive episodes during the same period.

Symptoms commonly include low mood, anhedonia, hypersomnia, increased appetite (especially craving carbohydrates), weight gain, and social withdrawal. These symptoms cause significant distress or impairment in social, occupational, or other important areas of functioning.

It is essential to exclude other psychiatric disorders or medical conditions that could explain the seasonal pattern of symptoms. The diagnosis is clinical, based on history and symptom pattern, as there are no definitive laboratory tests.

These criteria align with the ICD-10 and DSM-5 specifiers for seasonal pattern in major depressive disorder, as well as UK clinical guidelines on depression management. The literature emphasizes the importance of the temporal relationship of symptoms to seasons and the reproducibility of this pattern over multiple years (Magnusson and Partonen, 2005; Thaler et al., 2011) ¹.