Talking about demographic is complicated. Bastard! was serialized in a shōnen magazine, now it's in a seinen one. Just like MPD Psycho. And Shigurui, which is more gruesome than Berserk, is a shōnen, and the magazine in which it was serialized changed to a seinen. Pretty hard to put some of works into cases, and they're not isolated cases.
When I see some seinen works like Chi which don't have anything serious, I can say that demographic doesn't affect that much the content of works. As long as it's good. =P
But you're right on the catharsis part.