Q:  Can Head Injury Result in Bipolar Disorder?

  
My son had two concussions at age 17 within 3 weeks resulting from 2 car accidents (neither was his fault). We have had many diagnosis for him and the most recent is bipolar 1. Can this be the result of this type of injury? I thought it was hereditary. Before now neurologist have said he had PTSD, anxiety attacks, depression, post-concussion syndrome, etc. Now we have added this new diagnosis. Does this sound reasonable to you?

Dear Ms. M' -- 
Unfortunately, yes, this is reasonable: cases of bipolar disorder associated with head injury have been reported.  Here is an example (you could dig up the reference if you wish; note that the abstract points out this is rare):

JOURNAL OF THE AMERICAN ACADEMY OF CHILD & ADOLESCENT PSYCHIATRY 2000;39:525-528

ABSTRACT

A case of bipolar disorder subsequent to a mild head injury in a 15-year-old girl is reported. Review of the literature indicates that this is an extremely rare outcome. Lack of adequate follow-up studies makes it difficult to accurately predict type and severity of psychiatric outcome. Assessment and management involves ongoing consideration of both organic and psychosocial factors even after initial negative investigations.

Dr. Phelps