After reading more about it, I imagine it was probably his struggles since he's been in the league. Just think, football is your life. It defines you a human being. You're setting records in college. Your hopes are high. Your friends and family believe in you. Your future is bright. Then your put on IR two years in a row. Your future as a football player, the thing that defines your entire existence looks like it might be coming to an end. The sense of failure is overwhelming. Throw in mental illness and what happened happens.
Now I could be totally wrong. Maybe his girl left him. I don't know. But I'd be willing to bet that it's what I'm saying. I'll eat crow when I'm wrong.