Conditions · Mood
Seasonal affective disorder — NIMH overview
Why depression that arrives with the dark months is a distinct pattern, and what the evidence actually says about light therapy.
National Institute of Mental Health6 min read
NIMH's SAD page is careful about what is and is not known: the recurrent-winter pattern is well documented, the underlying mechanisms (circadian, serotonergic) are still being worked out, and bright-light therapy has reasonable evidence when used correctly.
Includes practical guidance on light boxes (intensity, timing, duration) that is often missing from consumer coverage.
Mental Hum's library is a curated index of authoritative third-party resources. The summary above is our own framing; the full information lives at the source.
A note on this article
Mental Hum publishes general education, not medical advice. If something here reflects your own experience, please consider speaking to a clinician. If you are in crisis, call or text 988.