I'm guessing you can afford spending $300 on light therapy glasses.
Disclaimer: I'm not a doctor, but saw 4 seasons of dr. House. Moreover, few hours of Huberman Lab on sleep and light and most importantly, this episode of Additude Mag Podcast on curing SAD and ADHD day-rhytm shifting with light glasses: https://www.youtube.com/watch?v=fu4mLgkNc6I
What happens in the seasonal affective disorder season is the sunlight pattern diverges from 6-18 that we evolved with. Without daily reminder of getting enough sun (or sun-like) light at the 6 o'clock⁰, your body clock will drift.
It can start by feeling groggy instead of refreshed in the morning, even if you've slept enough. And can escalate into loosing the will to do anything or even live.
No wonder. You're still an animal. You need to be fed, put to bed, etc. at a specific time. If you try to make your body sleep during the day, and eat and work during what body expects to be night, you won't really sleep and won't really live/work. Enough of not really sleeping and not really living - you mess up your body, your gut biome, your hormonal balance and your brain chemistry. You kind of should get depressed when you do it.
You can steer your body clock with light. Most of us do it, by exposing ourselves to strong (strong enough it won't matter if it includes blue wavelength or not).
But you can do it consciously (and in a way good for you) by putting on light therapy glasses (I'm using Lumiere 3¹, and they are not the only ones, find your own) at 6⁰ everyday, or right after you wake up if you're trying to readjust your rhythm. Or if you have time and want to save $200, use a stationary lamp and just sit in front of it doing nothing. I don't have the time. When readjusting, small doses of melatonin (0.5mg) 1h before sleep will accelerate body clock shift.
But don't listen to me, if you have SAD, you should really listen to that ADHD experts episode.
I feel for you, struggling with that stuff for a long time. Vit D, fish oil (lot of). All lights at home set to reduce intensity after 18. Strict going to bed routine. Still sleep poorly once in a while, but can do things in winter again. Hope it will help :)
0: choose whatever suits you. With small doses of melatonin and discipline in using light glasses you can even flip day and night. Just stay consistent, good farmer always feeds his cows at the same time.
1: at the time of buying ( fall '25 ) they were cheapest and best overall in norway. Solid build, ok battery, can have them on during yoga using attached rubbers and kind of can have them over glasses. Mine are very large and have blue light filter, but I manage 20min without eyeglasses. Medical certificate. Few leds, holo strip, battery and some plastic - my inner Scrooge says it's not worth $285, but everything else was worse and more expensive.