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

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.

To establish the SIMS failure rates in SUD patients, and examine the relationship between symptom validity, psychological distress, and performance validity.

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).

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.

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.