Cardiac autonomic balance as a treatment target and indicator of treatment response following an exercise intervention among young adults with depression: results from a secondary data analysis
Creators: name: Bocchine, Anthony J.
Publisher: name: No Publisher Supplied
Year: 2021

description: Major depressive disorder (MDD) is a prevalent neuropsychiatric disorder and a leading cause of worldwide disability. Depression is associated with debilitating symptoms and significant impairments to quality of life and exacts a significant burden to society. Although there are available treatment options, including pharmacological and cognitive behavioral therapy, remission rates remain low and treatment response is considerably variable. Furthermore, low diagnostic success rates for depression could be due in part to a lack of knowledge or consideration of unique psychophysiological processes that contribute to depression. There has been increasing research attention devoted to alternative or adjunctive treatments that do not carry the same challenges or limitations to pharmacological (e.g., tolerance, side effect profiles) and cognitive behavioral therapies (e.g., cost, accessibility). Accumulating evidence supports the efficacy of aerobic exercise as an alternative monotherapy or adjunct to conventional treatments for depression. However, treatment response rates to aerobic exercise are also variable underscoring the need to identify transdiagnostic intervention targets and predictors of treatment response to advance precision medicine approaches incorporating exercise for depression. One promising psychophysiological mechanism in depression can be captured by heart rate variability (HRV), or the variation between successive heart beats within the electrocardiogram. Dysregulation in sympathetic and parasympathetic branches of the autonomic nervous system (ANS), often indexed by alterations in HRV, has been examined within the context of major depression for decades. In the first aim, we examined resting levels of CAB before and following an 8-week aerobic exercise intervention among individuals with and without depression. Resting CAB was reduced in non-responders relative to responders of the aerobic exercise intervention. Secondary aims were to determine whether the magnitude of change in CAB from pre-to-post intervention was correlated with change in depressive symptoms and whether CAB at baseline could predict treatment response across 8 weeks of intervention with aerobic exercise or light stretching. No significant pre-to-post treatment changes were observed for any of the autonomic measures; however, pretreatment CAB was a marginally significant predictor of treatment response, net of baseline depressive symptoms, aerobic fitness, and body mass index. Collectively, these findings suggest that 8 weeks of aerobic exercise is effective for reducing depressive symptoms, although the observed symptom reductions are not accompanied by meaningful change in CAB, HF-HRV, or PEP. The marginally significant finding of baseline CAB as predictor of treatment response is noteworthy and potentially relevant for identifying patients most likely to benefit from exercise interventions.