Induction of acute stress through an internet-delivered Trier Social Stress Test as assessed by photoplethysmography on a smartphone
Recent studies have demonstrated the feasibility of administering the Trier Social Stress Test (TSST) through the internet, with major implications for promoting international inclusivity in research participation through extending typical sampling procedures beyond traditional geographical boundaries. However, online TSST studies to date are limited by the lack of a control group, which may be particularly problematic for studies administered through video mediated platforms, given evidence these interactions may be inherently stressful due to a minimization of nonverbal cues and overemphasis on facial expression. Furthermore, there is a need for biological measures of stress reactivity that can be fully implemented online, as extant research has relied upon laboratory measures that must be shipped back and forth between laboratory and participant. Here, we test smartphone-based photoplethysmography as a measure of heart rate reactivity to an online variant of the TSST. Results demonstrate significant acceleration in heart rate and self-reported stress and anxiety in the TSST condition relative to a placebo version of the TSST. The placebo procedures lead to a significant increase in self-reported stress and anxiety relative to baseline levels, but this increase was smaller in magnitude than that observed in the TSST condition. These findings highlight the potential for smartphone-based photoplethysmography in internet-delivered studies of cardiac reactivity and demonstrate that it is critical to utilize random assignment to a control or stressor condition when administering acute stress online.