Posttraumatic stress disorder (PTSD) is frequently comorbid with substance use disorder (SUD) in individuals seeking treatment for substance use. Further, SUD and PTSD are individually associated with cognitive impairment (CI) and poor treatment outcomes. Despite the frequent use of the Montreal Cognitive Assessment (MoCA) as a screening tool for CI, the validity of the MoCA has not been established in individuals with comorbid SUD-PTSD. We assessed the criterion validity of the MoCA in 128 participants seeking inpatient medically-assisted detoxification using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) as a reference for CI. The correlation between the RBANS and MoCA was weaker in those with SUD-PTSD (r = .32) relative to SUD alone (r = .56). Receiver operating characteristic (ROC) curves demonstrated that the MoCA had moderate-to-high ability to discriminate CI in individuals with SUD alone, with an area under the ROC curve of .82 (95% CI .69-.92) and optimal cutoff score of ≤23. However, in individuals with comorbid SUD-PTSD, the ROC analysis was not significant. Results suggest that PTSD, when comorbid with SUD, reduces the criterion-related validity of the MoCA. We recommend exercising caution when classifying CI in individuals with SUD-PTSD using the MoCA and suggest reducing the cutoff score to ≤23 in order to limit the rate of false-positive CI diagnoses in SUD-PTSD populations.
Keywords: Cognitive impairment; Montreal Cognitive Assessment (MoCA); cognitive screening; detoxification; neuropsychology.