What can I do to help my 17 year old son? He is withdrawn and depressed a lot of the time. More info provided?

Get him his own animal. Let him pick it out. When I was in the psychiatric hospital, they had pets and they made us feel a lot better. Coming from someone with clinical depression, it's hard to be upset when there's a puppy wildly twisting itself all around your legs :) Also, if he likes horses, take him to a local stable and ask about training and volunteering at the stable. Hope this helps and wishing the best for you and your son.