I'm a rapid cycler too but SAD feels different. I don't know how to explain it but it is different.

I have a light but I can only use it when I'm relatively stable or it shoots me into mania, even though I have one that lets me use really low settings. This year is definitely NOT a year I'll be using it, at least not for now.

I find that I get seasonal changes routinely. I get depressed in November and manic in June, every year. So maybe not typical SAD but definitely it is there.

I knew it was just a matter of time before the depression overtook my mixed episode and that's happening now. But I don't know how that will happen since my cycling for the past 11 months has been different than usual. I am not usually this anxious with SAD but that may change on its' own.

I kind of think if you question whether you have SAD you probably have it.