Long-term cognitive effects after SCG-DBS in patients with treatment resistant depression: A 5-year follow-up.

INTRODUCTION Cognitive symptoms represent a significant and persistent challenge in patients with treatment-resistant depression (TRD), substantially impacting their functional outcomes. Deep brain stimulation (DBS) targeting the subcallosal cingulate gyrus (SCG) has shown clinical efficacy. Nonetheless, its long-term effects on cognition remains insufficiently researched. This study systematically evaluates cognitive outcomes following SCG-DBS over an extended follow-up period.

Methods

This retrospective, exploratory secondary analysis used longitudinal data from 12 TRD patients treated with SCG-DBS without a control group. Cognitive and clinical assessments were conducted pre-surgery and at long-term follow-up. Potential changes were examined using the Wilcoxon signed-rank test and its corresponding effect size (r), while Reliable Change Indices (RCIs) were applied to evaluate the statistical reliability of intra-subject cognitive changes. Spearman correlations explored associations between cognitive outcomes with clinical and functional ones.

Results

After a median follow-up of 5 years following SCG-DBS, TRD patients showed statistically significant improvements in immediate and delayed verbal memory (Wilcoxon's z = -2.28, p = .023, r = 0.66; Wilcoxon's z = -2.83, p = .005, r = 0.82, respectively), both reflecting large effect sizes. RCIs indicated reliable improvement in immediate (41.7% of patients) and in delayed (75%) verbal memory. Changes in verbal memory were not significantly correlated with clinical or functional improvements.

Conclusions

These findings support the cognitive safety and benefits of SCG-DBS in individuals with TRD, particularly in verbal memory. However, further research is required to investigate the broader functional effects of SCG-DBS beyond the improvement of core clinical symptoms.