Depressive symptoms among stress-exposed youth: Relations with tonic and phasic indices of autonomic functioning.

Theoretical models of adolescent depression postulate that one possible individual vulnerability factor for the development of depressive symptoms is autonomic dysregulation. However, there is limited and mixed support for these models among ethnically diverse and higher risk stress-exposed youth. Therefore, this study investigated the relations between both tonic and phasic indices of parasympathetic autonomic functioning (i.e., resting high-frequency heart rate variability [HF-HRV] and root mean square of successive differences [RMSSD]; HF-HRV and RMSSD reactivity to a mental arithmetic stressor) and depressive symptoms among 80 severely stress-exposed youth (51% female; 11-17 years of age) from diverse backgrounds (61.3% ethnic minority; caregiver-reported median family income = $20,000-$49,999 per year). Results demonstrated that lower resting HF-HRV and RMSSD, but not HF-HRV and RMSSD reactivity, was associated with greater youth depressive symptoms. Our findings suggest that lower resting parasympathetic autonomic functioning may be a potential vulnerability factor of depressive symptoms among stress-exposed youth, instead of specific emotional responses to stressors. These findings will need to be replicated in larger samples of stress-exposed youth and youth at higher risk for or exhibiting clinical levels of depressive symptoms to better elucidate relations with autonomic functioning and depressive symptoms among adolescents.