What helps (I would think) with depression would be things like "fitting in", "feeling valid", "feeling purpose", "not feeling shame", ""not having social anxiety", "sleeping well", "being fit", "having a healthy community", "having fulfilling hobbies", "having a healthy friend group", "having healthy family relationships".
not "knowing more about how depression works".
I also don't believe that doctors really talk what the 'various causes are'.
I've been depressed, very much so, and I've read books that summarize scientific reading about depression like The Upward Spiral[0], and I feel like they miss the point, somehow. Like: we're great at finding treatments and things that work for individual people, but I sort-of think that the problem with depression is fundamentally everyone else, ie, 'society is sick', and we treat it as a personal problem because well of course doctors can't prescribe fixes to society, but they can for a person, so it's all stopgaps that don't address the "real problem".
I think that often depressed people have an idea of this -- that it is the existence around them that is sick, somehow -- and so no amount of suggestions (which indeed might actually help) quite gets to the bottom of that because it is the world that is fundamentally wrong. (Or specifically it is the nature of how they currently fit into the world.) From a treatment standpoint yes of course they should do the things that will probably help them, and people around them should be empowered to get them to do the things that will help them. But for the person that is struggling that really doesn't feel like the answer, and I think that they're not wrong.
(By 'society is sick' I mean that the person does not, for whatever reason, exist in the mentally healthy setting that their brain was 'designed' to exist in -- a healthy community, the right kinds of relationships, the emotional mentors and sources of wisdom that provide the right kinds of useful guidance, a body that works the way that it's supposed to, physically and mentally, etc; and a world around them that makes sense, that they can feasibly cope with, which is exactly the opposite of the nihilism induced by news of politics and global tragedies.)
[0]: (https://smile.amazon.com/Upward-Spiral-Neuroscience-Reverse-...)
"Don’t try to cheer him up or offer advice
... it could backfire by reinforcing his sense that you just don’t get it, said Megan Devine, a psychotherapist and the author of “It’s O.K. That You’re Not O.K.”
“Your job as a support person is not to cheer people up. It’s to acknowledge that it sucks right now, and their pain exists,” she said."
My parents also read a bunch of books on depression and tried to teach me about it to help me.
It was the last thing I wanted to do. I didn't have any energy to learn anything, I was having enough trouble trying to hold myself together as much as possible every day. Whenever someone tries to help someone who's depressed, I guess they don't get it because most of the time, the depressed person is probably barely keeping it together, and asking them for anything more is not going to work.