#KindnessbyPost: a pre-post, observational evaluation and feasibility study of a participatory public mental health intervention.

background#KindnessbyPost (KbP) is a "national kindness exchange". Participants send and receive a card by post to different, unknown people containing messages of good will. Previous evidence suggests participation in KbP may reduce loneliness and improve wellbeing. We evaluated the outcomes and administrative costs of KbP and explored the feasibility of collecting health economic measures for future research.

methodsWe used a pre-post, observational study design. Participants in two separate KbP exchanges in 2021 were invited to complete an online questionnaire. It included self-reported measures quantifying psychological wellbeing and loneliness, capability, and healthcare service use. Data were collected at three time-points per exchange: exchange-start (baseline), exchange-end (2 weeks), and 3 months post-exchange. Administrative cost data were obtained from the KbP programme organisers.

resultsAcross both exchanges, 1,285 responses were received from 1,142 participants. 143 participants completed questionnaires at both exchanges. In total, 623 (48%) participants completed follow-ups at exchange-end, and 414 (32%) at 3 months post-exchange. 70% (n = 789) of participants were aged between 31 and 60 years. 94% (n = 1,075) of participants were female and 95% (n = 1,078) were of white ethnicity. Compared to baseline, loneliness reduced and wellbeing increased at exchange end (change in loneliness = ‑0.21 units, 95% CI: -0.29 to -0.12; change in wellbeing = 0.68 units, 95% CI: 0.47 to 0.88, respectively) and at 3 months post-exchange (loneliness change = -0.40 units, 95% CI: -0.50 to -0.30; wellbeing change = 1.01 units, 95% CI: 0.77 to 1.25, respectively). Capability scores (mean (SD) were calculated at baseline: 0.74 (0.18); exchange-end: 0.75 (0.19); and 3 months: 0.76 (0.18)) from available responses. The average administrative cost of delivering the intervention was £0.67-£0.87 per participant, not including in-kind contributions.

conclusionsWe observed a small, sustained improvement to people's wellbeing and loneliness following participation in a KbP exchange. Given the study design, causal attribution to KbP is uncertain. However, our results are consistent with previous evaluations and offer preliminary evidence that KbP may be an effective mental wellbeing intervention. Given its low administrative cost and highly scalable design, KbP could also be a cost-effective intervention for improving public mental health, warranting definitive evaluation of effectiveness and cost-effectiveness in future. Our study also demonstrated the feasibility of collecting wellbeing and health economic outcome measures needed for future research.