Change in Cognitive Function over the Course of Major Depressive Disorder: A Systematic Review and Meta-analysis.

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Psychology

Background:

• Major depressive disorder (MDD) is linked to persistent cognitive impairments.
• These deficits impact individuals during both active illness and remission phases.

Purpose of the Study:

• To systematically review and meta-analyze the trajectory of cognitive function in MDD.
• To investigate how demographic, clinical, and treatment factors moderate cognitive changes over time.

Main Methods:

• A systematic search identified studies with a ≥12-week test-retest interval for cognitive function in MDD.
• Random effects modeling was used to pool data from 69 meta-analyzed studies (4639 patients).
• Cognitive changes were assessed across 44 variables, calculating effect sizes (Hedges' g).

Main Results:

• Over 95% of cognitive variables showed non-significant, negligible, or small improvements.
• Improvements were comparable to potential practice effects seen in healthy controls.
• Depressive symptom reduction and prior episode count moderated cognitive change, indicating state- and scar-like effects.

Conclusions:

• Cognitive changes in MDD are generally small following treatment.
• Cognitive recovery capacity may be diminished with increased episode recurrence.
• Early cognitive intervention in MDD could improve prognosis and functional recovery.