Track the pattern across seasons — that's your best clue

The clearest way to tell late-winter SAD from atypical depression is to track whether your symptoms repeat in a seasonal pattern over multiple years.

Both conditions can look nearly identical in February: sleeping 10 hours, craving carbs, feeling heavy and unmotivated. But SAD is tied to the calendar. If you’ve had the same slump for three winters in a row, and it lifts by May like clockwork — that’s SAD. Atypical depression, on the other hand, doesn’t follow a seasonal cycle. It might come and go randomly, or it might just stick around year-round without a summer break.

Another clue: how you respond to light. SAD usually improves with bright light therapy or even just getting outside more as days lengthen. If morning light or a lamp makes a dent, that leans SAD. If nothing changes, atypical depression is more likely.

One more subtle difference — SAD tends to hit hardest in the morning. Waking up feels impossible. Atypical depression can also involve morning sluggishness, but it often comes with a more persistent, non-seasonal heaviness that doesn’t shift with sunlight.

If you’re still unsure, keep a mood log through at least one spring and summer. If you feel genuinely better when the sun comes back, you’ve got your answer.