UC Merced

Objective: Theoretical work has proposed that acceptance, attention monitoring, decentering, self-compassion, and nonreactivity may be mechanisms that explain beneficial effects of mindfulness. Yet, our understanding of how mindfulness mechanisms operate in everyday life is limited. The goal of this dissertation is to examine the extent to which these mechanisms naturally vary in everyday life and following a smartphone app-based mindfulness intervention. Methods: A large-scale university-wide randomized controlled trial was conducted to test the effects of app-based mindfulness intervention (Headspace) on well- being of university employees (n = 143). The study utilized ecological momentary assessment design to measure mindfulness mechanisms in participants’ natural environment. Study 1 examined whether mindfulness mechanisms represent independent constructs that naturally vary within a person over time, and whether naturally occurring fluctuations in mindfulness mechanisms differentially predict negative emotions. Study 2 investigated how mindfulness mechanisms change over the course of an 8-week app- based mindfulness intervention, with mindfulness mechanisms assessed at week 0 (pre- treatment), week 2, week 5, and week 8. Results: For Study 1, multilevel factor analysis revealed four distinct mechanisms – acceptance-attention, decentering, self-compassion, and nonreactivity – that exhibit substantial moment-to-moment variation. Greater acceptance-attention, self-compassion, and nonreactivity were associated with lower negative emotions, while greater decentering predicted higher negative emotions when examined concurrently with the other mechanisms. Study 2 found that improvements in acceptance-attention, decentering, and nonreactivity occurred after two weeks of the intervention. These mechanisms continued improving steadily over the course of the 8-week intervention. Conclusions: These findings highlight that not all mindfulness mechanisms may similarly relate to the same health outcomes. Although significant improvements in mindfulness mechanisms occur after two weeks of mindfulness intervention, these effects compound over time suggesting that longer intervention format can lead to greater improvements in mindfulness mechanisms compared to shorter programs. Finally, the findings demonstrate that app-based mindfulness interventions can effectively teach mindfulness mechanisms and provide a suitable alternative for people who cannot access traditional in-person mindfulness interventions.