Category: Adult Anxiety - GAD
Introduction. Heart rate variability (HRV), or the fluctuations in time intervals between heartbeats, has been conceptualized as an indicator of autonomic nervous system flexibility. Lower HRV has been associated with chronic hypervigilance and with lower performance on executive tasks involved in adjusting behavioural responses to environmental demands. In Generalized Anxiety Disorder (GAD), reduced resting HRV has been associated with the presence of excessive worry. Objective. The goal of this study is to explore the impact of cognitive-behavioural therapy (CBT) on HRV in adults with GAD. Hypotheses. We predicted (1) that participants would show a significant increase in HRV following treatment; and (2) that change in HRV would be significantly correlated with changes in GAD symptoms and in level of worry. Participants. All participants are at least 18 years old, have a primary diagnosis of GAD and have agreed to keep medication status stable while participating in the study. Measures. The Penn State Worry Questionnaire is a self-report measure that assesses chronic, uncontrollable and excessive worry (16 items, 5-point Likert scale). The Anxiety and Related Disorders Interview Schedule for DSM-IV is a diagnostic interview that assesses all anxiety disorders and their severity (9-point Likert scale). For HRV measurement, participants were fitted with a telemetric interbeat interval recorder (Polar RX800) using a sampling rate of 1000 samples per second. Procedure. Data are from an ongoing clinical trial of cognitive-behavioural therapy for adults with GAD (n = 35 currently, n = 45 expected by November 2017). All participants completed 12 weekly 50-minute treatment sessions of an innovative single-component treatment: behavioural experiments for intolerance to uncertainty. Each participant was assessed at pre- and post-treatment. Physiological data was recorded during a 10-minute resting baseline while participants watched a relaxing video. For the HRV assessment, participants were asked to refrain from smoking, drinking caffeinated beverages and exercising for at least two hours prior to the recordings. Statistical analyses. To test the hypotheses, we will compute a paired samples t-test and correlations using residual change scores.