A Systematic Review and Meta-Analysis of Cognitive Training in Adults with Major Depressive Disorder.

Major Depressive Disorder (MDD) is common and disabling, and is linked to functional impairment and increased mortality. While current treatments for MDD are moderately effective, ultimately, up to one third of patients do not achieve full remission. Interestingly, while affective symptoms of major depression typically resolve with the depressive episode, cognitive impairment frequently persists, and has been identified as one of the most prominent predictors of illness recurrence. Additionally, MDD is well-recognised as a key risk factor for further cognitive decline and dementia. Yet, available treatments for MDD do not typically address cognitive impairment. Cognitive training, represents a promising and novel therapeutic intervention in this regard. This review systematically identified and evaluated the evidence for cognitive training in adults with MDD. Following PRISMA guidelines, eligible studies were selected according to pre-defined criteria delineating our target population (adults with clinically defined MDD), parameters for cognitive training interventions (computer-or strategy-based, clinician-facilitated), and study design (controlled trials including pre-post cognitive and psychological or functional outcome data). Of 448 studies identified, nine studies met inclusion criteria. These studies were evaluated for methodological quality and risk of bias. Despite heterogeneity, qualitative and meta-analytic synthesis of study findings revealed significant improvements in cognitive and affective outcomes following cognitive training, with moderate pooled effect sizes. Unfortunately, very few studies investigated 'far transfer' to broader domains of everyday functioning. Overall, given the strong evidence for the efficacy and value of cognitive training in this context, cognitive training should be considered as a primary therapeutic intervention in the treatment of MDD.