Pain, malingering and the WAIS-III Working Memory Index

Background contextPain patients often report cognitive symptoms, and many will include them in their claims of disability. There is empirical evidence that patients with pain do experience problems on attention-demanding cognitive tasks, but the results are mixed and the potential impact of exaggeration in the context of pain-related litigation has not been addressed.Purpose1) Examine the impact of pain and malingering on attention; 2) determine if the Working Memory Index (WMI) of the Wechsler Adult Intelligence Scale-3 (WAIS-III) can reliably detect malingering.Study design/settingStudy 1: simulator design; Study 2: clinical known-groups design.Patient sampleStudy 1 used healthy college students; Study 2 used chronic pain patients and neurological patients.Outcome measuresThe WMI and its constituent subtests.MethodsStudy 1: College students were administered the WMI under three conditions: standard administration, with cold-pressor induced pain, or with instructions to simulate impairment due to pain. Study 2: Known-groups design in which the WMI was examined in nonmalingering and definite malingering chronic pain patients, nonmalingering moderate–severe traumatic brain injury, and memory disorder patients seen for routine psychological evaluation. Malingering was operationalized using published criteria.ResultsThere were no group differences in WMI or its subtests among nonmalingering groups, but some individual clinical patients with pain did score at a level suggestive of attentional impairment. The lowest scores were found in the simulated malingering college students and definite malingering clinical pain groups, in which about half scored worse than 95% of the nonmalingering clinical patients.ConclusionsThis study demonstrated that even when controlling for exaggeration some pain patients do exhibit problems with attentional function. However, significant impairment in WMI performance (eg, index score≤70), particularly in the absence of brain dysfunction, cannot reasonably be attributed to the effects of either acute or chronic pain, even at moderate to severe levels, and likely reflects intentional exaggeration.