MBSR effects on positive psychological traits and experiential avoidance in head and neck cancer: a randomized controlled trial

<b>Background:</b> Data on the effects of mindfulness-based stress reduction (MBSR) positive psychological traits and experiential avoidance (EA) among cancer patients are lacking.<b>Objective:</b> This randomized controlled trial (RCT) aimed to: (1) compare the efficacy between MBSR and treatment-as-usual (TAU) control groups in increasing posttraumatic growth (PTG), hope, and optimism and reducing EA across time measurements (T₀, T₁, and T₂) among head and neck cancer (HNC) patients and (2) evaluate the mediation effects of hope, optimism, and EA on the relationship between MBSR and PTG.<b>Methods:</b> A total of 80 HNC participants were randomized to MBSR (<i>n</i> = 40) and TAU (<i>n</i> = 40) groups with the researchers and data analyst blinded, and the group allocation of the participants was concealed. A one-hour MBSR session was conducted once a week, with 45 minutes of home assignments, for six weeks in the MBSR group. The outcomes across time measurements were compared using a mixed linear model following intention-to-treat (ITT) analysis. Mediation effects of hope, optimism, and EA on the relationship between MBSR and PTG were assessed with PROCESS.<b>Results:</b> MBSR significantly increased the degree of optimism from T₀ to T₁ (mean difference = 1.825, 95% CI = 0.907-2.743, SE = 0.381, <i>p</i> < .001) with a medium effect size (<i>d</i> = 0.563) and from T₁ to T₂ (mean difference = 1.650, 95% CI = 0.829-2.470, SE = 0.328, <i>p</i> < .001) with a medium effect size (<i>d</i> = 0.630). Initially, MBSR did not increase the degree of hope from T₀ to T₁ (<i>p</i> = .677), but it significantly increased hope from T₁ to T₂ (mean difference = 2.524, 95% CI = 1.676-3.373, SE = 0.340, <i>p</i> < .001) with a medium effect size (<i>d</i> = 0.735). Conversely, MBSR did not sustain the changes in the degree of PTG and EA beyond T₁. EA partially mediated the relationship between MBSR and PTG, but not hope and optimism.<b>Conclusion:</b> MBSR can be recommended as part of the treatment regimen for HNC patients.<b>Trial registration:</b> ClinicalTrials.gov identifier: NCT04800419.