Cognitive impairment among the dually-diagnosed: substance use history and depressive symptom correlates

The present study examined the effects of substance use history and depressive symptomatology on the cognitive functioning of 149 male and 72 female dually diagnosed inpatients. Logistic regression models examined the effects of life-time alcohol and cocaine use, previous month's alcohol and cocaine use and depression on abstract reasoning as assessed by the Shipley Institute of Living Scale (SILS) and neuropsychological functioning as measured by the Screening Test for the Luria-Nebraska Neuropsychological Battery (ST-LNNB). Results indicated differential effects of substance use across the two cognitive outcome measures. Specifically, a significant relationship was demonstrated for previous month's alcohol use on Shipley classification. However, after adjusting for possible borderline cases, previous month's alcohol use dropped to non-significance and in its stead an association between Shipley classification and life-time use was demonstrated. No significant effects were demonstrated for cocaine use, recent alcohol use, depressive symptoms or any of the interaction terms. The Luria-Nebraska performance classifications were significantly associated with both educational level and life-time cocaine use. No significant relationships were obtained for previous month's cocaine use, the alcohol use variables, depressive symptoms, or any of the interactions terms. The degree of classification agreement between the two outcome measures was slightly better than chance (kappa = 0.24 for ST-LNNB and traditional or full scale SILS; kappa = 0.35 for ST-LNNB and modified SILS). These kappa coefficients suggest that the SILS and ST-LNNB assess partially independent dimensions of cognitive functioning. The findings are discussed in light of previous research and implications for clinical assessment and treatment are outlined.