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.

Prevalence and characteristics of depression in mild cognitive impairment: the Sydney Memory and Ageing Study

OBJECTIVE

Depression might be a risk factor for dementia. However, little is known about the prevalence of depressive symptoms in mild cognitive impairment (MCI) and whether mood or motivation-related symptoms are predominant.

METHOD

A total of 767 non-demented community-dwelling adults aged 70-90 years completed a comprehensive assessment, including neuropsychological testing, and a past psychiatric/medical history interview. Depressive symptoms were assessed using the Geriatric Depression Scale (GDS) and Kessler Psychological Distress Scale (K10). Exploratory factor analysis was performed on the GDS and K10 to derive 'mood' and 'motivation' subscales.

RESULTS

A total of 290 participants were classified as having MCI and 468 as cognitively normal (CN). Participants with MCI reported more depressive symptoms, and more MCI participants met the cut-off for clinically significant symptoms, relative to CN participants. Those with amnestic MCI (aMCI), but not non-amnestic MCI, had more depressive symptoms and were more likely to meet the cut-off for clinically significant depressive symptoms, relative to CN participants. Participants with MCI reported more mood-related symptoms than CN participants, while there were no differences between groups on motivation-related symptoms.

CONCLUSION

Individuals with MCI, especially aMCI, endorse more depressive symptoms when compared with cognitively intact individuals. These findings highlight the importance of assessing and treating depressive symptoms in MCI.