A Comparative Analysis of Symptom and Performance Validity in Substance Use Disorder.

BACKGROUND: Symptom validity assessment is crucial in clinical neuropsychology, especially in populations prone to under- or overreporting, such as patients with Substance Use Disorders (SUD). This study investigated symptom validity using the Structured Inventory of Malingered Symptomatology (SIMS) in a SUD inpatient population. OBJECTIVES: To establish the SIMS failure rates in SUD patients, and examine the relationship between symptom validity, psychological distress, and performance validity. METHODS: Retrospective data were analyzed from 55 patients with SUD admitted to a closed addiction ward. Symptom validity was measured with the SIMS, psychological distress with the Symptom Checklist-90-Revised (SCL-90-R), and performance validity with the Visual Association Test - Extended (VAT-E). RESULTS: Using the traditional SIMS cutoff (>16), 32.7% of patients exceeded the threshold, compared to 12.7% using a more conservative cutoff (>23). SIMS total scores showed a strong positive correlation with psychological distress (SCL-90-R total; ρ = 0.71, p < 0.001), and weak agreement between SIMS and SCL-90-R classifications (κ = 0.46, p < 0.001) when using a liberal cutoff, and minimal agreement using a more conservative cutoff (κ = 0.17, p = 0.026). No significant associations were observed between SIMS scores and VAT-E indices of performance validity. CONCLUSIONS: Elevated SIMS scores were relatively common in this SUD sample and were strongly associated with self-reported psychological distress, while showing no relationship with performance validity. These findings highlight the conceptual distinction between symptom validity and performance validity and underscore the importance of a multimethod approach when assessing response validity in patients with SUDs.