>Not everyone on this board can have a depression disorder, can they?Well, it's certainly possible — just not likely. Keep in mind, it's not that everyone here is depressed, or even that everyone who becomes a NEET is depressed. In fact, if you ask me, depression is a spectrum, and it's only when a person becomes symptomatic enough that they are considered "clinically" depressed.
My point is, people seek out places where they can find others with whom they have something in common. Because there
are some depressed people here, it will naturally attract other people who are depressed. They commiserate, and the feeling of hopelessness amplifies. Eventually it becomes an echo chamber; with enough people talking about the tough times they've been through or are currently going through, it becomes the dominant subject matter. Although not everyone is necessarily clinically depressed, most everyone has had something bad happen to them. So — when they're all concentrated in one place, sharing with each other the worst of experiences of their lives in order to relate to one another — it appears that everyone posting is abjectly depressed.
Also, like
>>11778 said, the NEET life itself attracts the depressed and socially disinclined. And this board, while ostensibly not just about being NEET, will of course have quite a few NEET posters.