I'm writing this, because I'm at my wits end about what to do. I know there's some of you out there who's been battling depression and similar things, or maybe know someone in the same situation, so maybe you can help me out regarding what to do.

My younger brother is turning 18 this year, and just started his final year of High School. He's been tired of school since three years back and has been skipping classes and such, having his grades drop dramatically during this time. Before he started High School, he was a relatively happy-go-lucky guy that would always hang out with me and my sister, and we would go out and do stuff together all the time. But lately, he's changed so much, and I'm not sure why.

He's very into gaming, and spends most of his waking hours eating candy, drinking soda, and playing LoL and WoW. Now, I don't mind gaming at all, since I do it myself on a regular basis, but it's the quantity of it that might not be healthy. If something goes wrong in the game, he'll slam the desk and shout various obsceneties at the game - and this shows as well when he's practicing driving. He'll spend half the time yelling at people driving around him how stupid they are, and how idiotic humanity is in general. He's just very angry, almost all the time. Daily he'll drop comments on how worthless everything is and that there's no point in doing anything. I haven't seen him smile or laugh in months, which just breaks my heart.

I've tried getting him to tag along to the gym or for a walk, just to get out and do something else and get some exercise, but he just gets upset and believes that's my way of telling him he needs to work out. I've told him various times that that's not it, that we can go go-carting or play mini-golf or bowling or whatever, just so he can get out and do something other than sitting locked in his room in the basement. That I'm worried about how he's feeling. Me (and my family) have tried getting him to tag along to things - the cinema, going out to eat, going on day-trips... But he refuses, every time. Everything is boring and "worthless". And I don't know what else to do, I can't physically drag him out of the house, unfortunately...

We were talking about something yesterday, can't remember what, and I said "Oh, well when you get a job you can do that" and he said "Well, we all know that won't happen"... And I was absolutely stunned. He's got no trust in himself, he's lost all sense of self-worth for some reason. He doesn't have a vision for the future - I never hear him talk about what he want to do when he's done with High School, or talk about dreams or whatever. And whenever I ask, I just get a mumbling answer like "dunno", and he goes back to lock himself in his room.

I'm worried he might be depressed, or something along those lines. And I don't know what to do. I feel like a terrible big sister for not being able to do anything about it. I've told him that if he wants to, I can help him book a time with a counselor or something, someone he can talk to - but whenever I mention it I just get the answer that "What? No! I'm not insane, I'm not crazy, I don't need to talk to anyone", and then the silent treatment for days. My younger sister has spent many nights crying, because she misses her older brother that used to take her out to do stuff - but now, the only communication they have is whenever he shouts at her for doing something wrong.

I just don't know what to do anymore, and it pains me to see him like this.