Bipolar disorder is an epigenetic disorder. See the documentary "the ghost in our genes" its free on youtube to get familiar with the issue.
If he is open, energy therapies are much more effective than conventional therapy, for example EMDR, EFT, TAT or WHEE.
I personally use BSFF deveolped by Dr. Larry Nims.
BPD is not my specialty, but I have helped clients with it. If you wish to work with someone with more experience, I recommend Gilbert Renaud. He has a website and works with Skype or over the telephone.