Functional and cognitive impairment in the first episode of depression: A systematic review

Objectives To describe the cognitive and functional impairment in individuals with the first episode of major depressive disorder (MDD) as compared to controls and individuals with recurrent MDD. Also to describe the functional and cognitive trajectory after the first episode of MDD. Methods A total of 52 studies were included in our systematic review. 32 studies compared the cognitive performance between first episode of depression (FED) and controls, 11 studies compared the cognitive performance between recurrent depression (RD) and FED, 10 compared global functioning between RD and FED, four studies assessed cognition in FED over time, and two studies assessed global functioning in FED over time. Results The majority of studies (n = 22/32, 68.8%) found that FED subjects performed significantly worse than controls on cognitive tests, with processing speed (n = 12) and executive/working memory (n = 11) being the most commonly impaired domains. Seven out of 11 studies (63.6%) found that RD performed significantly worse than FED, with verbal learning and memory being the most commonly impaired domain (n = 4). Most studies (n = 7/10, 70%) did not find a significant difference in global functioning between RD and FED. In three of four longitudinal studies assessing cognition, subgroup analyses were used instead of directly assessing cognition in FED over time while the remaining study found significant cognitive declines over time in FED when compared to controls. The two longitudinal studies assessing functional trajectory found that functioning significantly improved over time, possibly due to the improvement of depressive symptoms. Conclusion There is strong evidence that cognitive impairment is present during the first episode of depression, and individuals with multiple episodes display greater cognitive impairment than individuals with a single episode. Future studies aimed at identifying predictors of cognitive and functional impairment after the first episode of depression are needed to describe the functional and cognitive trajectory of individuals with the first episode of MDD over time.