RESUMO
BACKGROUND: Frontline nurses suffered unprecedented mental distress during the COVID-19 pandemic. It's essential to explore new and more accessible alternatives to improve the availability of psychological treatments. This study aimed to investigate the influence of online self-help iACT linear intervention and iACT loop intervention on sleep quality (SQ), obsessive-compulsive symptoms (OCS), and psychological flexibility (PF) in nurses. METHODS: A randomized controlled trial was conducted at a hospital in China. 602 participants were randomly assigned to the iACT linear intervention, iACT loop intervention, or wait list control group, and required to complete the questionnaires of OCS, PF and SQ. The linear mixed effects analysis (LMM) was used to analyze the impact of the intervention on outcome variables. RESULTS: LMM analyses demonstrated that both two intervention had significant improvement on OCS (t = -38.235, p < 0.001), PF (t = 28.156, p < 0.001), as well as SQ (t = -16.336, p < 0.001). There were significant differences between the linear group and loop group on the PF in T2 (t = -8.271, p < 0.001), T3 (t = -8.366, p < 0.001), T4 (t = -8.302, p < 0.001), with the iACT loop model (Cohen's d = 1.652) showing a slight advantage over the iACT linear model (Cohen's d = 1.134). CONCLUSIONS: The findings indicate that two interventions positively impact OCS, PF, and SQ. Compared to the iACT linear psychotherapy model, the iACT loop model shows greater effectiveness in enhancing PF, making it helpful to promote significant improvements in psychotherapy planning.