Hot and cold neuropsychological impairment in severe depression

Abstract

Neuropsychological impairment is a core feature of major depression. However, the exact nature of this impairment is unclear. Although deficits in traditional ‘cold’measures of neuropsychological functioning (memory, attention, executive functioning) have been reported in a number of studies ofmajor depression, less research has focused on emotional or ‘hot’ processing. There is evidence that hot neuropsychological processing is impaired to a greater extent than cold processing in bipolar depression. The aim of the current study was to determine which neuropsychological domains showed the greatest impairment in severe major depression, with a particular focus on comparing hot and cold neuropsychological measures. Sixty-eight severely depressed inpatients were compared with 50 healthy controls on a broad range of hot (facial emotion processing) and cold neuropsychological tasks. Effect sizes (Cohen's d) were calculated for the differences between groups in each task in order to compare the magnitude of impairment. Depressed patients showed impairment across all of the neuropsychological domains tested and these differences were not caused by psychotropic medication use in the patients. Measures that produced particularly robust effects sizes were verbal learning (0.81) and recognition (1.07), visuospatial memory (0.81), verbal fluency (1.08), Stroop task interference (0.84) and psychomotor speed (0.85). The largest effect size produced from several measures in the facial emotion processing tasks was a specifically impaired recognition of disgusted facial expressions in the depressed group compared with the healthy control group (0.72). The present study does not indicate that depressed patients show greater impairment on emotional neuropsychological tasks compared with traditional, non-emotional neuropsychological tasks; in fact, the findings suggest that the opposite is the case. This has important implications for understanding the brain mechanisms underlying major depression.