Methods: This study is nested within a randomized controlled trial of a Coping Power adaptation for middle school youth with aggressive behavior problems. During 10 of the 25 weekly sessions physiological data was collected via wristband, and youth also self-reported their engagement using a 10-item survey (alpha = .75; response range: 1-4). Data are analyzed on 152 students over the course of 884 group sessions. Linear regression with clustered variance estimates was used to examine overall trends in association between HRV and self-reported engagement, as well as unique associations by session. We hypothesized session-specific effects in which session content would predict different heart rate patterns.
Results: Self-reported engagement was high, with mean scores ranging from 3.1 to 3.4 across sessions. Mean heart rates (HR) were centered around 91-92 beats per minute. As expected, preliminary results suggest no consistent across-session association between self-reported engagement and either HR or HRV; instead, we observed more nuanced effects. Youth who reported feeling comfortable in session had consistently lower mean HR (β = -.63, p=.019), whereas youth who reported getting angry at a peer had no significant difference in mean HR (β = .14, p=.464), but did have greater HRV (β = .30, p=.012), suggesting that they were physiologically triggered by the interaction. After controlling for mean HR, self-reported engagement was associated with significantly lower HRV in two sessions requiring a high level of activity (session 15: β = -1.10, p=.006; session 25: β = -1.14, p=.030), whereas in a session with less activity, engagement was associated with marginally higher HRV (session 24: β = .81, p=.053).
Conclusions: Physiological indicators of arousal may provide valuable information in preventive interventions, but must be interpreted within the context of intervention components and their expected effect. Challenges and strategies for the use of physiological indicators will be discussed.