I just know that it's a semi-autobiography of Dazai's, and is reported as one of his greatest novels. My partner who introduced me to the book did say that people have a sense of anxiety, depression, or (tw) suicidal ideation after reading, and a lot of people seem to think it's because the author soon after writing this did, sadly, end his life.

I'm currently reasoning that it most likely has something to do with the fact that you're supposed to feel the same thing the point of view is feeling, similar to what you said.