Neurocognitive subgroups in major depressive disorder

Background: Major depressive disorder (MDD) is commonly associated with neurocognitive dysfunction. However, there remains substantial heterogeneity between patients and inconsistent findings regarding the magnitude and prevalence of specific neurocognitive deficits. This study aimed to investigate the potential for different neurocognitive subgroups in patients diagnosed with MDD. Method: Data were pooled from 4 different clinical trials that involved adults diagnosed with MDD. Neurocognitive outcomes included measures of verbal learning and memory, executive function, attention, and processing speed. Latent class analysis was conducted to examine for different subgroups based on neurocognitive profiles of performance across outcome measures. Subgroups were compared to a separate sample of age-matched adult healthy controls, across illness factors, and individual mood items on the Montgomery-Asberg Depression Rating Scale (MADRS). Results: Within the MDD cohort (N = 149), 45% of participants were considered relatively "cognitively preserved, " with the remainder "cognitively reduced" (39%) or "cognitively impaired" (16%). Verbal memory performance was significantly poorer compared to attention and processing speed only in the "cognitively impaired" subgroup. There was no association between subgroup membership and relevant illness factors, including ratings on individual MADRS items. Limitations: Data were pooled from several studies that included different neurocognitive measures and cohorts. Conclusions: Approximately half of MDD participants had no or minimal objective cognitive difficulties, and neurocognitive functioning was found generally unrelated to illness factors. Future longitudinal research is warranted to determine whether the people who are relatively cognitively impaired are at increased risk for further cognitive decline.