Is suboptimal effort an issue? A systematic review on neuropsychological performance validity in major depressive disorder.

BACKGROUND:In Major Depressive Disorder (MDD), emotion- and motivation related symptoms may affect effort during neuropsychological testing. Performance Validity Tests (PVT's) are therefore essential, but are rarely mentioned in research on cognitive functioning in MDD. We aimed to assess the proportion of MDD patients with demonstrated valid performance and determine cognitive functioning in patients with valid performance. This is the first systematic review on neuropsychological performance validity in MDD. METHODS:Databases PubMed, PsycINFO, Embase, and Cochrane Library were searched for studies reporting on PVT results of adult MDD patients. We meta-analyzed the proportion of MDD patients with PVT scores indicative of valid performance. RESULTS:Seven studies with a total of 409 MDD patients fulfilled inclusion criteria. Six studies reported the exact proportion of patients with PVT scores indicative of valid performance, which ranged from 60 to 100 % with a proportion estimate of 94 %. Four studies reported on cognitive functioning in MDD patients with valid performance. Two out of these studies found memory impairment in a minority of MDD patients and two out of these studies found no cognitive impairment. LIMITATIONS:Small number of studies and small sample sizes. CONCLUSIONS:A surprisingly small number of studies reported on PVT in MDD. About 94 % of MDD patients in studies using PVT's had valid neuropsychological test performance. Concessive information regarding cognitive functioning in MDD patients with valid performance was lacking. Neuropsychological performance validity should be taken into account since this may alter conclusions regarding cognitive functioning.