The Summer 2012 issue of Bipolar magazine (Bipolar Disorder Magazine | Bipolar Symptoms | bphope) did a feature on this topic. Yes, it can definitely be related to the bipolar and typically gets worse as our illnesses progress. My pdoc has me on an amino acid called N-acetylcysteine (abbreviated as NAC) specifically for the cognitive issues and it seems to help. The meds can certainly contribute to it, but I'm afraid that it is also the nature of the illness itself.