Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of Disorder, seasonal affective (SAD)
Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026
Disorder, seasonal affective (SAD): Depression that tends to occur (and recur) as the days grow shorter in the fall and winter. It is believed that affected persons react adversely to the decreasing amounts of light and the colder temperatures as the fall and winter progress.
Seasonal affective disorder has not been recognized very long as a medical condition. The term first appeared in print in 1985. Seasonal affective disorder is also sometimes called winter depression or the hibernation reaction.