My partner has frequent bouts of depression where she just feels ambiently sad for no particular reason, often to the point of crying. These bouts can last anywhere from a few hours to a few days. In total I'd estimate that she spends about 1/6 of her waking time depressed, though I haven't been keeping careful track. This has been happening for many years.
She's currently 35, exercises for about an hour most mornings, mostly healthy though with a few dietary issues. She's talked to a doctor and has been taking fluoxetine, but it hasn't seemed to help. She's open to experimentation but will have trouble sticking to anything super consistent.
If anyone suggests something that seems to have permanently solved the problem, I'll pay you M$1,000,000 or $1000 USD, your choice.
1,000People are also trading
Professional help should be a safe bet, but I doubt this'll suffice for a bounty
I suppose you know the rationalist standard literature: https://www.astralcodexten.com/p/peer-review-request-depression
Personally, I'm trying to get my mother (chronic depression, several medications and therapies) to try psilocybin. I can try to explain why I could imagine magic mushrooms to help if that's within "open to experimentation"
I feel like when I saw the movie I Heart Huckabees for the first time it partially alleviated my depression/existential dread/whatever you want to call it.
But I didn't know that it would do that when I sat down to watch it and maybe if my expectations had been raised to that level it would have ruined the experience.