The impact of substance use disorder comorbidity on cognition of individuals with bipolar disorder: A systematic review

The aim of this study is to describe whether Bipolar Disorder (BD) with Substance Use Disorder (SUD) comorbidity is associated with an increased cognitive impairment as compared to BD without SUD comorbidity. This is a systematic review. The literature search was conducted in three databases: PubMed, PsycINFO and Embase. A total of 2032 studies were screened after removing duplicates. 29 articles were included for full text screening, and a total of 14 articles were included in the systematic review. Multiple cognitive domains were assessed, including verbal, spatial and visual memory, and psychomotor and executive functioning. Over half the articles (64.3%, n=9) identified cognitive impairments in individuals with BD+SUD comorbidity as compared to individuals with BD without SUD comorbidity. In addition, individuals with the comorbidity exhibited more severe impairments on tests of executive functioning, and greater impairments in verbal and visual memory. The studies included in this systematic review reinforce that individual with comorbidity of BD and SUD have increased cognitive impairment as compared to individuals with BD without SUD comorbidity. Executive functioning was the most impaired cognitive domain found across the studies included in this review. Intervention strategies focused on executive functioning would be beneficial for this specific population.