To put it as simple as possible..drugs.
That, and I believe he is also brain-injured. I had read somewhere that at a local house party he was given the boots pretty good.
Everything I have heard/read sounds exactly like a friend of mine. This friend was an amazing athlete, shy, drinking at a booze can, talking to a girl when said girl's boyfriend flew into jealous rage and boot stomped him with his friends.
In the years since then, my friend had told me that sometimes, he just didn't 'feel right', like he was experiencing things, but just not remembering them. All sorts of odd behavious--combined with drug use led to some of the most entertaining and sad behaviours.
I feel bad as drugs are seemingly his and Steven's 'escape' from their pain.
Brain injuries are no joke. Combined with drugs....