Relationships among Cognition, Symptom Validity, and Self-Reported Disability

Objective: Disability and functioning are central aspects of neuropsychological and psychological evaluations. Disability is often assessed by self-report measures, such as the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0), which are only marginally related to objective cognitive functioning, and more strongly related to depression and psychiatric symptom severity. In many settings, the accuracy of a patient’s responding (symptom validity) may be called into question, particularly when there is an identified or possible external incentive. It was hypothesized that symptom validity would moderate the relationship of cognition and disability, and that failure of a symptom validity test (SVT), the MMPI-2-RF Infrequent Somatic Complaints scale, would be associated with greater self-reported disability. Methods: This study examined the interrelationships among depression, cognition, symptom validity, and self-reported disability in a sample of Veterans undergoing evaluation for seizure disorders at the Michael E. DeBakey VA Medical Center Epilepsy Monitoring Unit. Structural equation modeling approaches were used to examine the extent to which depression, cognition, and symptom validity predict self-reported disability. Follow-up analyses including means comparisons and chi square tests were used to detect group differences in symptom endorsement as well as associated demographic factors. Results: Structural equation modeling analyses indicated that depression was the strongest predictor of self-reported disability, accounting for almost all of the variance explained. There was no evidence of a moderating effect of symptom validity on the relationship between objective cognitive performance and self-reported disability. Models which excluded depression revealed that symptom validity is moderately predictive of self-reported disability. Subjects who failed SVTs were more likely to report greater disability and symptom severity across self-report instruments. Diagnosis was associated with SVT failure such that patients with psychogenic nonepileptic events were more likely to fail SVT than patients with epilepsy. Conclusions: The study added to a growing literature on the utility of self-reported disability by providing further evidence that objective cognitive performance is not associated with perceived disability, whereas levels of depression, and to a lesser extent, the tendency to report infrequent symptoms, are more strongly related. Self-report of disability should therefore be interpreted with caution, and in the context of psychiatric factors.