Cognitive Functioning in the First-Episode of Major Depressive Disorder: A Systematic Review and Meta-Analysis

Objective: Cognitive deficits are frequently observed in major depression. Yet, when these deficits emerge and how they relate to the depressed state is unclear. The aim of this 2-part systematic review and meta-analysis is to determine the pattern and extent of cognitive deficits during a first-episode of depression (FED) and their persistence following FED remission. Method: Published, peer-reviewed articles on cognitive function in FED patients through October 2015 were searched. Meta-analyses with random-effects modeling were conducted. Part 1 assessed weighted, mean effect sizes of cognitive function in FED patients relative to healthy controls. Moderator analyses of clinical and demographical variables effects were conducted. Part 2 assessed weighted, mean effect sizes of change in cognitive function at remission compared with acute FED performance in longitudinal studies. Results: Thirty-one studies including 994 FED patients were retained in Part 1. Relative to healthy controls, small to large impairments were observed across most cognitive domains. Remission was associated with a normalization of function in processing speed, learning and memory, autobiographical memory, shifting, and IQ. Lower FED age was associated with higher IQ, but more impairment in word-list delayed memory. Four studies including 92 FED patients were retained in Part 2. Following remission, FED patients showed small improvements in processing speed and shifting but persistent impairment in inhibition and verbal fluency. Conclusion: Significant cognitive deficits are already identifiable during a FED, with some functions showing persistent impairment upon remission. Clinicians must consider cognitive impairment alongside mood symptoms to ensure functional recovery from the FED.