Timing and full remission are what matter for SAD.

The DSM-5 seasonal pattern specifier helps by requiring a clear temporal relationship between depressive episodes and a specific season, plus full remission between episodes, which usually rules out non-seasonal depression that just happens to occur in winter.

The specifier is strict: depressive episodes must have a regular onset at a particular time of year (e.g., fall or winter) and complete remission at another (e.g., spring). You also need at least two consecutive years with no non-seasonal episodes during that period. So if