Evaluation of the effects of severe depression on global cognitive function and memory

Introduction: Major depressive disorder (MDD) is thought to negatively impact cognitive function; however, the relationship has not been well explored. Objective: This study examined the association between depression severity and global cognitive function and memory in subjects with severe, treatment-resistant MDD. Methods: We enrolled 66 subjects with Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosed unipolar MDD in a multicenter trial to assess the efficacy and neurocognitive effects of electroconvulsive therapy (ECT). We measured depression severity with the 24 item Hamilton Rating Scale for Depression (HRSD₂₄). Neuropsychologic measures included the Mini Mental State Examination (MMSE), Rey Auditory Verbal Learning Test (RAVLT), and the Complex Figure Test (CFT). Correlational and regression analyses were conducted to explore associations between depression severity and cognitive function. Results: The mean age of the subjects was 53.6 years (SD=15.8), 65% were female, and mean HRSD₂₄ was 33.9 (SD=6.7). Mean demographic-corrected T-scores for each neurocognitive measure were in the average to borderline range, and HRSD₂₄ values were unrelated to performance on the MMSE, RAVLT immediate and delayed recall, and CFT immediate and delayed recall. Conclusion: In this sample of severely depressed subjects referred for ECT, depression severity was unrelated to global cognitive function or memory. Future research should examine the interactions between other depressive characteristics and neurocognitive function.