Who Should I be Kind to? A Randomized Controlled Trial about Practicing Kindness for Strong and Weak Social Ties and its Specific Mechanisms of Change

The beneficial impact of practicing kindness has been thoroughly examined, but little is known about how its social mechanisms might affect mental health outcomes. It is also unclear how the popular ‘acts of kindness’ intervention works and which type of instructions works best for whom. Therefore, the first aim of the current trial (N = 222) was to explore whether a 4-week acts of kindness intervention targeting either (1) strong social ties, (2) weak social ties or (3) unspecified receivers (i.e., kindness as usual) improves mental well-being, positive relations, depressive symptoms, anxiety, and perceived stress. The second aim was to explore whether positive emotions and self-esteem mediated the effects and whether the effects are moderated by baseline levels of self-esteem and positive relations. Results of paired t-tests demonstrated that the interventions led to improvements in mental well-being, but also in increased psychological distress. ANCOVA analyses revealed only marginal improvements in mental well-being in favor of kindness for strong social ties. There was also no combined mediation effect of self-esteem and positive emotions. However, moderation analyses revealed that mental well-being reduced significantly more in participants who performed kind acts for weak social ties, but only when self-esteem was medium or high. Overall, practicing kindness for others seemed beneficial for students’ mental well-being—especially when kindness was directed towards strong social ties— but also led to a deterioration of psychological distress. More research is needed to examine when and for whom practicing kindness is beneficial or detrimental.