Tailoring Gratitude Interventions. How and for Whom Do They Work? The Potential Mediating Role of Reward Processing and the Moderating Role of Childhood Adversity and Trait Gratitude

Outcomes of gratitude interventions are encouraging, but inconsistent across studies. In addition, both mechanisms of change and effect modifiers for these interventions are largely unknown. Recent data point toward potential candidates and suggest reward processing may be a promising mechanism underlying these interventions, while childhood adversity (CA) and trait gratitude may impact on them. However, existing research aimed at investigating these hypotheses is scarce. Building on these, we examined the effectiveness of a gratitude intervention for decreasing depressive symptoms and negative affect and increasing positive affect. We also investigated changes in reward processing following intervention and explored differences in adherence and drop-out between groups. Finally, we investigated the moderating role of CA and trait gratitude. Participants (N=237, ages between 18-56) were randomly allocated to a gratitude or active control condition (14 days). Following intervention, findings indicated a significant decrease in depressive symptoms and negative affect in both conditions. While positive affect remained stable, a significant time effect emerged for reward processing. CA severity, but not multiplicity, moderated the effectiveness of the intervention, adherence and drop-out. Trait gratitude moderated the effectiveness of the gratitude intervention only on depressive symptoms. Gratitude interventions may not be the best fit for everyone. Thus, we recommend tailoring interventions, especially in individuals reporting a history of severe CA.