What is seasonal depression and when does it start?
Last updated September 3, 2026.
SAD is major depression that follows the calendar - usually starting in fall as days shorten, deepening through winter, lifting in spring. NIMH describes the winter-pattern cluster: oversleeping, carb craving, weight gain, heavy fatigue, withdrawal. The line between winter blues and SAD: the blues are common and mild; SAD seriously affects how you feel, think, and function, and recurs with the seasons. It is very treatable - light therapy, psychotherapy, medication, and vitamin D are the four listed categories.
What to do
- Track two winters. The recurrence across consecutive seasons is the diagnostic signature.
- Start treatment in early fall. Getting ahead of the pattern beats catching up to it.
- Push the daylight basics. Morning outdoor light, regular sleep-wake, and movement all measurably help.
- Get evaluated before buying gear. Confirm the pattern before buying gear. In crisis: 988 in the US, or your local crisis line.
Related questions
- Do light boxes actually work for SAD?
- How do I know if I'm depressed?
- Why do I feel worse at night?
- What is burnout vs depression?