Was Chris' head injury more significant than it might seem?

Feels like after Chris got smacked in the head with the shovel pretty badly in Pine Barrens that he started going downhill.

Before that episode he managed to:
-Get clean off drugs
-Get made and move up in the family
-Learn from his mistakes and improve
-Be a good partner to Adriana

Afterwards everything possible that could go wrong for him, does go wrong, mostly because of his own decisions.