Depressed children with asthma evidence increased airway resistance: "vagal bias" as a mechanism?

BACKGROUND: Depression is prevalent in pediatric asthma, and implicated in asthma morbidity and mortality. Pathways linking stress, depression, and asthma are unknown.
OBJECTIVES: To examine, under controlled laboratory conditions, pathways by which depressive states affect airway function via autonomic dysregulation.
METHODS: Participants were 171 children with asthma, age 7 to 17 years, presenting to an emergency department for asthma exacerbation. Forty-five children with asthma and high depressive symptoms (D) were contrasted with 45 with low/no depressive symptoms (ND). Depressive symptoms, asthma disease severity, vagal and sympathetic reactivity to film stressors, airflow (FEV1), and airway resistance were compared between the groups. A subgroup with greater airway reactivity (nonmedicated FEV1<80% predicted) was also studied. Correlations among variables were examined for the entire sample.
RESULTS: Groups did not differ in demographics, disease severity, medications, or adherence. The D group with FEV1<80% predicted showed greater airway resistance throughout all conditions (P = .03), and vagal bias in the film stressors. The D group's vagal response was significant for the sad stimuli: family distress/loss (P = .03), dying (P = .003), and death (P = .03). The ND group showed sympathetic activation to sad stimuli: lonely (P = .04) and dying (P = .04). Depressive symptoms were correlated with respiratory resistance (r = .43; P = .001) and vagal bias in scene 3 (r = .24; P = .03), and vagal bias (scene 3) was correlated with postmovie airway resistance (r = 0.39; P = .004).
CONCLUSIONS: Children with asthma and depressive symptoms manifest vagal bias when emotionally stressed. Those with depressive symptoms and FEV1<80% manifest greater airway resistance. Depression, vagal bias, and airway resistance were intercorrelated for the full sample.