I suspect from his writings undiagnosed (and untreated) bipolar - the descriptions of the depression, the tour de force creativity runs. I could be seeing this through bipolar-coloured glasses, of course - I don't have bipolar, but I have loved ones who do. It's scary shit, and frequently really hard to treat in any effective manner.
I think his self-ideal must have been, a person who solves problems, important problems that need solving. And that is why he didn't seek help. Perhaps he was used to solving problems by himself, perhaps he didn't even trust other people to solve them correctly. So he simply ignored or endured the depression and the physical illness when they occurred. And he managed to survive that lifestyle for his first ten years as a hacktivist, but eventually he ran up against something that he couldn't topple or dodge, so in the end he chose that solution which also offers final relief.
Link
One of us is no more.
He deserves a eulogy more eloquent than what I am capable of writing. Here's Cory Doctorow's, one of his long time friends.
It's a sad world in which you are being arrested and grand jury'd for downloading scientific journals and papers with the intent to share them.