Psychiatric comorbidity is extremely common. One of the most common and difficult to manage comorbid conditions is the co-occurrence of bipolar disorder (BD) and obsessive compulsive disorder (OCD). We updated our recent systematic review searching the electronic databases MEDLINE, Embase, and PsycINFO to investigate course of illness in BD–OCD patients. We identified a total of 13 relevant papers which found that the majority of comorbid OCD cases appeared to be related to mood episodes. OC symptoms in comorbid patients appeared more often during depressive episodes, and comorbid BD and OCD cycled together, with OC symptoms often remitting during manic/hypomanic episodes.