UBC Theses and Dissertations
Depression and anxiety : differing relationships to respiratory sinus arrhythmia Hibbert, Anita S.
Many theoretical models addressing the role of the parasympathetic branch of the autonomic nervous system in psychopathology predict decreased respiratory sinus arrhythmia (RSA) in disorders such as depression and anxiety. However, decreased RSA in depression is not consistently observed across studies. Research on the relationship between anxiety and RSA has also been mixed, but the results may be more robust than that of depression. Before the theoretical models can be re-examined based on these findings, researchers must clarify the nature of these relationships. Specifically, three things should be determined: a) is there a relationship between RSA and depression; b) is there a relationship between anxiety and RSA; and c) could comorbid anxiety in depression be playing a role in the mixed findings to date. This study was specifically designed to address those three questions. Based on the empirical literature, we hypothesized that: 1) depression would have a small but significant relationship to RSA; 2) anxiety would have a significant relationship to RSA that would be stronger than that of depression to RSA; 3) the anxiety-RSA relationship would persist when controlling for depression, whereas the depression-RSA relationship would not persist when controlling for anxiety. Additionally, the Cardiac Sympathetic Index (CSI) was used to explore the potential relationships that depression and anxiety may have with sympathetic-related heart rate variability and sympathovagal balance. One-hundred and twenty-eight physically healthy undergraduate students completed a questionnaire measure assessing depression and anxiety symptoms. Participants’ ECG recordings were taken both at rest and during a stressful arithmetic task to obtain measures of RSA and CSI. Regression analysis revealed a significant inverse relationship between anxiety and RSA, and a marginally significant inverse relationship between depression and RSA, during the stressful arithmetic task. No significant relationships were observed at rest, or with CSI. Importantly, the relationship between anxiety and RSA persisted when controlling for depression, whereas the opposite was not true: the relationship between depression and RSA is almost eliminated when controlling for anxiety. These results suggest that some of the positive findings in the depression- RSA literature may be due to uncontrolled, co-occurring anxiety symptoms.
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