I agree completely, anon. It's always bothered me that his depression in the fifth book was never properly addressed and that fans write it off as him being annoying and too whiny. As a person, Harry is flawed. Yeah he's a hero, but he's still just a kid, a boy who was abused growing up and then had the weight of the world placed on his shoulders. People died at Voldemort's hand, and in a way he will probably always believe that some of them died because of him.

Depression comes in many forms, Harry's was rage. I think part of the problem is the way our society views depression and how limited anyone's knowledge of serious things like PTSD is. Not only did Harry see someone die, he never got to properly grieve or cope with that loss and the guilt that came with Cedric's death. And then the feelings that came with Sirius' I feel he just pushed far down so he wouldn't have to deal and so he wouldn't make the same mistake. Plus, right after Sirius' death he's dumped with the prophecy.