Varying levels of cognitive impairment have been recognized in bipolar disorder (BPD) patients. Higher educational attainment has been associated with lower cognitive impairment in BPD patients. This speaks to the concept of cognitive reserve, which reflects the brain’s ability to minimize the effect of psychopathology on outcomes, such as cognition. Substance abuse, a major comorbidity in BPD, can exacerbate cognitive impairments. In this study, we examined the associations between recent drug abuse and performance on several cognitive domains in BPD, and whether education, a proxy for cognitive reserve, moderates these associations. BPD outpatients (n=262, ages 18-65, 50.4% female) completed the MATRICS Consensus Cognitive Battery and the California Verbal Learning Test-II. The Drug Abuse Screen Test-10 was used as an index of drug abuse problems over the last year. All cognitive scores were normalized for age and sex. Higher levels of problematic drug use were associated with worse working memory (β=-.131, p=.036), visual learning (β=-.141, p=.023), and verbal learning (β=-.158, p=.011). Moderation analyses revealed a significant interaction between problematic drug abuse and education for working memory (β=.134, p=.042). These results show that the association between drug abuse and worse working memory was more pronounced in those with lower education level.
Many bipolar disorder (BPD) patients experience cognitive impairment (e.g., trouble remembering, concentrating, learning new things). Higher educational attainment is associated with lower cognitive impairment in BPD patients. This speaks to the concept of cognitive reserve, or the brain’s ability to minimize negative effects of diagnoses such as BPD on outcomes such as cognition. Substance abuse is a common issue within the BPD population. It is not known whether education, a cognitive reserve factor, affects the relationship between drug abuse and cognition in BPD patients. In this study, we examined 1) the associations between drug abuse and cognitive performance, and 2) whether educational attainment affects these associations in 264 BPD patients. Higher levels of problematic drug abuse in the past year were linked to worse cognitive performance. Education affected this relationship for one cognitive outcome of working memory (i.e., the amount of information that can be held in the mind temporarily to complete tasks). The association between drug abuse and worse working memory was evident in those with lower levels of education. These findings suggest that higher cognitive reserve, measured by education, may reduce the negative effects of substance abuse on working memory in BPD patients.