My opinion its usually external factors that the depressed person is or chooses to be powerless to control. Me personally I'd blame things like family issues especially when I was younger or the government abruptly shutting down most of what made up my life. Getting through it by perhaps seeing others frustrated on the internet or venting to that one friend who just says "yeah I get it" whether they do or not and spends time goofing around and taking your mind off it. Eventually I work it out in my head and move on. Try to learn from the experience.

I see in a lot of people they must have an external reason that they have no part in for everything. Extended tiredness must be "long Covid" and couldn't possibly be diet and exercise. Depression can't be because they won't stand up for themselves (even at a price) in a toxic relationship but it must be an external chemical imbalance they can get drugged away. Or no you couldn't possibly just be awkward because you're growing up, you must really be a boy in a girls body.

I'm not trying to necessarily blame people for their problems. Sure, there's the straight teen surrounded by parents and teachers who are tranny groomers or plenty of other examples of being stuck between a rock and a hard place, just my observations a lot of people can't answer the simple question of "What are you doing to improve your situation?" Without demanding a quick fix when one doesn't exist.