The Covid-19 pandemic has had many negative consequences on the general public mental health. The aim of this study was to test the effectiveness of and satisfaction with an app with gratitude exercises to improve the mental health of people with reduced mental well-being due to the Covid-19 pandemic, as well as potential mechanisms of well-being change and dose–response relationships. A two-armed randomized controlled trial design was used, with two groups receiving the 6-week gratitude intervention app either immediately (intervention group, n = 424) or after 6 weeks (waiting list control group, n = 425). Assessments took place online at baseline (T0), six weeks later (T1) and at 12 weeks (T2), measuring outcomes (i.e., mental well-being, anxiety, depression, stress), and potential explanatory variables (i.e., gratitude, positive reframing, rumination). Linear mixed models analyses showed that when controlled for baseline measures, the intervention group scored better on all outcome measures compared to the control group at T1 (d = .24–.49). These effects were maintained at T2. The control group scored equally well on all outcome measures at T2 after following the intervention. Effects of the intervention on well-being were partially explained by gratitude, positive reframing, and rumination, and finishing a greater number of modules was weakly related to better outcomes. The intervention was generally appealing, with some room for improvement. The results suggest that a mobile gratitude intervention app is a satisfactory and effective way to improve the mental health of the general population during the difficult times of a pandemic.

Covid-19 大流行对公众的心理健康产生了许多负面影响。本研究的目的是测试带有感恩练习的应用程序的有效性和满意度，以改善因 Covid-19 大流行而精神健康状况下降的人们的心理健康，以及幸福感变化的潜在机制和剂量反应关系。使用双臂随机对照试验设计，两组立即接受为期 6 周的感恩干预应用程序（干预组，n  = 424）或 6 周后（等待名单对照组，n = 425）。评估在基线 (T0)、六周后 (T1) 和 12 周 (T2) 时在线进行，测量结果（即心理健康、焦虑、抑郁、压力）和潜在的解释变量（即感恩、积极的重构、反思）。线性混合模型分析表明，当控制基线指标时，干预组在所有结果指标上的得分均优于 T1 时的对照组（d = .24–.49）。这些影响保持在 T2。干预后，对照组在 T2 的所有结果指标上得分相同。干预对幸福感的影响部分可以用感恩、积极的重构和反思来解释，完成更多的模块与更好的结果关系不大。干预措施总体上很有吸引力，但仍有一些改进空间。结果表明，移动感恩干预应用程序是一种令人满意且有效的方法，可以在大流行的困难时期改善普通人群的心理健康。