An evaluation of the impact of co-occurring anxiety and substance use disorder on bipolar disorder illness outcomes in STEP-BD.

backgroundAnxiety disorder (AD) and substance use disorder (SUD) highly co-occur with bipolar disorder (BD). AD and/or SUD co-occurrence is associated with poorer clinical outcomes in BD. However, respective associations between AD and/or SUD diagnoses and BD outcomes require clarification. Baseline data from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) were therefore utilized to investigate independent and simultaneous contributions of ADs and SUDs on clinical variables in BD.

methodsTwo latent factors, "pathological anxiety" and "substance use problems," were derived from presence/absence of lifetime AD and SUD diagnoses. Latent dimensions' associations with clinical variables, obtained from the Affective Disorders Evaluation, Mini-International Neuropsychiatric Interview and Range of Impaired Functioning, were estimated via structural equation modeling (SEM).

resultsModeled independently, pathological anxiety and substance use problems were significantly associated with several variables. Yet when modeled simultaneously, pathological anxiety's associations with functional impairment, past-year rapid cycling, and past-year %time spent anxious and depressed remained while most variables' associations with substance use problems became non-significant. The only significant latent-factor interaction evidenced was for age of BD onset. LIMITATIONS: Analyses were limited to lifetime diagnoses and causality may not be inferred given cross-sectional data.

conclusionsADs and SUDs impact on BD was mostly additive rather than synergistic. Findings highlight the potentially understated importance of treating inter-episodic anxiety in BD as it may exacerbate mood symptoms, increasing functional impairment and risk for subsequent mood episodes.