Are we exaggerating neuropsychological impairment in depression? Reopening a closed chapter

BACKGROUND: Meta-analyses conclude that individuals with depression display neurocognitive deficits. However, the extent to which some of these impairments occur due to secondary influences, and thus in part represent epiphenomena, has rarely been tested. Therefore, the authors examined the impact of performance motivation, attitude towards cognitive assessment, and momentary symptoms during assessment on neuropsychological test results in depression.

RESEARCH DESIGN AND METHODS: Forty-five patients with depression and 60 nonclinical individuals underwent a comprehensive neuropsychological test battery. Before and after the assessment, each participant was asked to complete the Momentary Influences, Attitudes and Motivation Impact on Cognitive Performance Scale (MIAMI).

RESULTS: As hypothesized, patients with depression performed worse than nonclinical controls on most neuropsychological parameters. Group differences achieved a medium effect size for parameters tapping speed and a large effect for parameters tapping accuracy. Yet, only one fourth of the patient population displayed abnormal scores (≥ 1 SD below the population mean). In line with the hypothesis, patients with depression were more fearful of test outcomes, complained more about negative momentary influences, and were less motivated (based on retrospective assessment) than controls, as assessed with the MIAMI. The MIAMI total score mediated the relationship between group status and test scores in three out of four analyses. When MIAMI scores were entered as covariate, group differences were largely reduced.

DISCUSSION: Patients with depression show a more negative attitude towards testing, lower performance motivation, and more negative momentary influences, all of which induce malperformance. The results suggest that performance dysfunction does not necessarily mirror brain dysfunction in areas hosting cognitive functions but is confounded with other factors. Greater caution is warranted when interpreting the results of neuropsychological tests in depressed patients.