A meta-scientific approach to understanding stress regulation

In the present Ph.D. project, I examined the efficacy of four strategies (i.e., self-administeredmindfulness, biofeedback, being in nature, and emotional social support) on stress reduction of individuals. To examine the empirical robustness of stress regulation strategies, we conducted two meta-analyses of the literature on these strategies, and one multi-site study experimentally examining the effect of one of the strategies (self-administered mindfulness) on stress regulation.In chapter 2, I present the result of a Registered Report meta-analysis in which we appraised the available evidence of being in nature and emotional social support on stress levels. After applying our publication bias correction techniques, we found an effect for the former strategy but not for the latter one. In chapter 3, I conducted a pre-registered meta-analysis that investigated whether two internal regulation strategies (i.e., self-administered mindfulness and biofeedback) could be considered reliable strategies for regulating stress levels. We found no evidence for the reduction of stress levels for these two strategies. Finally, in chapter 4, I present the results of a highly powered multi-site study thatinvestigated the efficacy of four single, brief stand-alone mindfulness exercises (versus three active control conditions) on self-reported experiences of stress in a population unfamiliar with mindfulness meditation. Results of the multi-site study provided evidence that participants had lower levels of self-reported levels of stress when they listened to one of the mindfulness exercises compared to those that were in the control conditions. In both meta-analyses, the high heterogeneity, the low-quality of the included studies, and the presence of publication bias cast doubts on the strength of evidence behind the studied effects. For what concerns the multi-site project, even if we cannot exclude the presence of a demand effect, our results hold promise for the efficacy of self-administered mindfulness interventions for the downregulation of stress. Taken together these studies suggest that stress levels can be reduced by relying on strategies that are non-pharmacological, non-invasive, and low-cost. Future studies (preferably in the form of Registered Reports) should try to make up for these shortcomings of the literature with well-powered studies and with the use of physiological measurements that could reduce the problem of the demand effect for studies on mindfulness.