A systematic review of gratitude interventions: Effects on physical health and health behaviors.

Objective: Gratitude interventions are easy-to-deliver, offering promise for use in clinical-care. Although gratitude interventions have consistently shown benefits to psychological wellbeing, the effects on physical health outcomes are mixed. This systematic review aims to synthesize gratitude intervention studies which assessed physical health and health behavior outcomes, as well as evaluate study quality, comment on their efficacy, and provide directions for future research.

Methods: Relevant studies were identified through searches conducted in PsycINFO, MedLine, Embase and Cochrane Library databases, up until August 2019. Only studies that evaluated a gratitude intervention, randomly assigned participants to gratitude and control conditions, and assessed objective and subjective measures of physical health and health behaviors were included. The Revised Cochrane risk-of-bias (RoB2) tool was used to assess risk of bias.

Results: Of the 1433 articles found, 19 were included in the review. Subjective sleep quality was improved in 5/8 studies. Improvements in blood pressure, glycemic control, asthma control and eating behavior were understudied yet demonstrated improvements (all 1/1). Other outcome categories remain understudied and mixed, such as inflammation markers (1/2) and self-reported physical symptoms (2/8). The majority of studies showed some risk of bias concerns.

Conclusions: Although it was suggested gratitude interventions may improve subjective sleep quality, more research is still needed to make firm conclusions on the efficacy of gratitude interventions on improving health outcomes. Further research focusing on gratitude's link with sleep and causal mechanisms is needed, especially in patient populations where more 'clinically-usable' psychosocial interventions are urgently needed.