AUTHOR=Sarlon Jan , Brühl Annette B. , Lang Undine E. , Kordon Andreas 

TITLE=Electrophysiological correlates of mindfulness in patients with major depressive disorder

JOURNAL=Frontiers in Neuroscience

VOLUME=Volume 16 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2022.971958

DOI=10.3389/fnins.2022.971958

ISSN=1662-453X

ABSTRACT=ABSTRACT
Objectives
Mindfulness-based interventions can reduce both stress and depressive symptoms. However, the impact of state mindfulness on stress level in depressed subjects remains unclear. The aim of this study was to assess electrophysiological correlates of state mindfulness in patients with major depressive disorder (MDD) at baseline, under stress exposure and in relaxation following stress exposure. 
Methods
State mindfulness was assessed with the Freiburger Mindfulness Inventory (FMI) in 89 inpatients (mean age 51) with MDD (mean BDI 30). Electrophysiological parameters (resting heart rate, heart rate variability, respiration rate, skin conductance and skin temperature) were recorded at five-minute baseline, one minute stress exposure and five-minute self-induced relaxation.  
Results
FMI was strongly inversely correlated with symptom severity measured by BDI (r= -0.53, p < 0.001). No correlations between FM score and electrophysiological parameters in any of the three conditions (baseline, stress exposure, relaxed state) could be found. The factor openness was associated with higher VLF in baseline condition. However, this correlation was no more significant after regression analysis when corrected for respiratory rate, age and sex. 
Conclusions 
Autonomous nervous reactivity in depression was not associated with state mindfulness as measured by FMI score and presented electrophysiological parameters, despite the strong inverse correlation between state mindfulness and symptom severity. According to our results, this association is primary not mediated by stress level or autonomous nervous reactivity.