A Cross-Sectional Study on the Relationship between Cardiorespiratory Fitness, Inhibitory Control, and Event-Related Potentials Moderated by Severity of Symptoms in Patients with Major Depressive Disorder

Background: Depression affects around 280 million people globally, with a lifetime prevalence of 20% for Major Depressive Disorder (MDD). Core MDD symptoms are impaired executive functions (EF), such as inhibitory cognitive control. Higher cardiorespiratory fitness (CRF) is linked to improved cognitive function, but whether this also applies to MDD patients remains unclear.Methods: This study examined the relationship between CRF and inhibitory control in 66 MDD patients (33 females, aged 18-63). Participants underwent VO2max testing after completing a flanker task while event-related potentials (ERPs) (N1, N2, P3) were assessed. Hierarchical multiple linear regressions were used to analyze the influence of CRF on flanker performance and ERP components, controlling for MDD severity, negative affect, and demographic variables.Results: CRF explained 15% of the variance in flanker performance (∆R² = .15, p < .001), with the final model (including all variables) explaining 47%. This positive effect of CRF was independent of MDD severity. Concerning the ERP correlates, CRF showed a medium effect on N1 latency at O1 (β = -.32, p = .04, ∆R² = .07, p = .04) with shorter latency in fitter individuals.Limitations: The study's cross-sectional design and moderate sample size limits causal inference. Conclusions: CRF was positively related to inhibitory cognitive control in MDD patients, independent of symptom severity, suggesting cognitive benefits. Earlier N1-peaks in fitter individuals suggest potential higher neural efficiency. Limited associations with ERP components indicate complex neural mechanisms, warranting further research. MDD treatments integrating physical exercise could contribute to improving cognitive health and mitigate decline.