To whom should I be kind? A randomized trial about kindness for strong and weak social ties on mental wellbeing and its specific mechanisms of change

The current study examines the role of social ties in performing kind acts to enhance university students’ wellbeing. Due to facing multifaceted challenges, university students form a group that is particularly vulnerable in terms of their mental health. Interventions harnessing prosocial behaviour have the potential to increase students’ wellbeing, strengthen personal competencies, and broaden social networks. The first aim of the 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 (treatment-as-usual) differ in their impact on students’ mental wellbeing, positive relations, depressive symptoms, anxiety, and perceived stress. The second aim was to examine whether kindness for strong versus weak social ties have different underlying working mechanisms (i.e., positive emotions versus self-esteem) and who benefits most from these instructions (i.e., those with high or low levels of self-esteem and positive relations). Results demonstrated that the most significant improvements in mental wellbeing were found in the kindness for strong social ties condition compared to the other conditions. No mediation effects of positive emotions and self-esteem were found. Moderation analyses revealed that participants who performed kind acts for weak social ties reported significantly less positive effects on mental wellbeing, but only when their levels of self-esteem at baseline were medium or high. Independent of group allocation, participants’ mental wellbeing increased throughout the intervention, but so did the experience of depressive symptoms, anxiety, and perceived stress. More research is needed to examine the timing of kindness interventions and investigate how they can improve mental wellbeing and psychological distress in acute phases of academic stress in university students.