Of the many things that can be said about this combination of problems, for now I just wanted to mention a few:

  1. Yes, they can occur together. Here’s a particularly good description by Dr. Russ Federman.
  2.  Mood experts generally agree:  “treat the bipolar first”. Get the mood part stable then treat whatever OCD remains. Sometimes, there won’t be any left, suggesting that it really wasn’t OCD but perhaps just part of the bipolar disorder (common, in my experience).
  3. The treatment for OCD is usually “high dose serotonergic antidepressants”. This can make bipolar disorder worse. Fortunately there’s another powerful treatment for OCD, though it’s challenging to do, and sometimes hard to find. It’s OCD-specific psychotherapy.
  4. So, putting all that together: if it seems like a person has both OCD and bipolar disorder, in general the approach would be to treat the mood part first.  If OCD symptoms remain, treat that with OCD-specific psychotherapy first if possible.  Offhand I can’t think of a case where I had to resort to antidepressants after all…