Here is something I copied from the site.
Manage Your Type O
The legacy of your Type O
ancestry causes an immediate “fight or flight” response in people of this blood type. However, this finely tuned response to stress, so vital in early Type O’s, is not always so beneficial in modern times. The Type O response can cause bouts of excessive anger, temper tantrums, hyperactivity and even create a severe enough chemical imbalance to bring about a MANIC episode.