Abstract
This study investigated whether gender moderates the effects of online mindfulness-based interventions (MBIs) on mental health outcomes in non-clinical populations. Specifically, we explored gender-related patterns in emotion regulation and cognitive flexibility. Data were obtained from a randomised controlled trial employing a crossover design in 2022 and 2023. Three hundred Japanese workers employed for at least 20 h weekly were randomly allocated to either an intervention or a waitlist group. The participants engaged in a four-week, app-based MBI involving daily guided practices, including brief breathing and body-scan meditations, with either loving-kindness or open-monitoring components. Perceived stress, anger, psychological flexibility, self-esteem, and emotion regulation were assessed at baseline and immediately after the four-week intervention or waitlist period. Interaction analyses between groups and gender revealed significant effects for cognitive flexibility (p = 0.023, partial η(2) = 0.018) and angry reaction (p = 0.007, partial η(2) = 0.025), although these findings did not survive correction for multiple testing. Exploratory simple slope analyses showed women showed greater cognitive flexibility (p = 0.034, Cohen’s d = 0.36) and reduced angry reactions (p < 0.001, Cohen’s d = −0.56), whereas men showed no significant changes in either variable (p = 0.202, Cohen’s d = -0.29 and p = 0.350, Cohen’s d = 0.22, respectively). This study tentatively suggests that brief online MBIs in preventive contexts may be associated with greater improvements in cognitive flexibility, with exploratory patterns indicating possible gender-related heterogeneity. However, these gender-related patterns should be interpreted cautiously. Considering individual differences, including gender, may help guide future preregistered personalisation research of digital psychological interventions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1038/s41598-026-46317-z.