Like clockwork, every year. Usually happens 2 or 3 weeks both before and after the winter solstice.
I try to make sure I’m getting plenty of vitamin D. And I try to make sure I’m getting outside for a bit everyday. Exercise helps a lot too - anything that’ll get your blood flowing and heart pumping.
I also make a rule for myself that I’m not allowed to make any big decisions or big commitments during that time of year because the depression can cloud my judgement. Not making commitments is hard with the holidays tho, so if I have to I also leave myself a way out of them if needed. I’ve become an expert at giving a “definite maybe” in response to commitments lol
IME there is an additional mental fog during the fall and winter seasons. I think there are a handful of reasons that are mostly a byproduct of shorter days and colder temps. More barriers to going outside when it’s cold (more layers, jackets), less social gatherings during the season, it being dark so early limits outdoor activities. Being able to do more helps my mental health for sure, which is much easier in the summer months.
Edit after seeing other comments: I was able to reach a “toxic” level of vitamin D last time I tried it, daily headaches, even just following the recommended amount. It took me a while to realize what was going on. I might have to try again with a smaller dose though.
I have to agree, it bothers me every year, but I take a high dose vitamin d supplement, make sure I get out for an hour at least at lunchtime, also bought a wake up light alarm which helps in the mornings