I am going to say I believe there is something to this. I read the 'Eat Right 4 Your Type' book and also purchased the Ailments book to go with it. I looked up Bi-Polar and a small graph proved type O was predominant for that as well as having issues with the brain and dopamine levels. Go to the main website, just search Blood Type Diet and there is an overview of type O and even there he briefly explains the science behind Type O's being predisposed to the 'fight or flight' response and references to brain chemicals.

Ornate Design
Let Food Be Your Medicine (may be more to that then we thought )