Whats he like normally? like when he doesnt want to do anything is he angry? depressed? sad? or just boring?
i have a friend who seems to be really depressed that i worry about alot. he hasnt said anything about suicide, but the last year or so he has basically turned into a huge asshole, around everyone he knows and thats nice to him. he never wants to do anything, and literally does nothing fun all day. the only "fun" he has is when he's drinking, and he's not even happy then, more like just not as depressed and pissed off. and thats a fucked up way to be, when you have to rely on dumbing your self down to not be depressed.
if i were you, i would really try to get him to get out and do something other than just hang out and party. that shit can make people depressed, when they realize that the highlight of their life is sitting around with company, then sitting around getting drunk. go camping, mountain biking, go shoot guns, or light off fireworks, something super active. he probably needs something to show him that its very easy for life not to suck ass.
and the whole wake up, work, sit around, party, lifestyle is not the answer.
if you cant do that for some reason, then id tell his parents.