Impact of Developmental Stage on Responses to a School-Based Mindfulness Intervention

The .b (“dot be”) mindfulness program aims to reduce both internalizing and externalizing risks and to enhance well-being among adolescents. A UK-based feasibility study (FS) reported significant improvements in depressive symptoms, stress, and well-being, whereas a large-scale randomized controlled trial—the UK-based MYRIAD study (MS) found no improvements and even some negative outcomes. To assess whether developmental stage might play an explanatory role in these discrepancies, we evaluated and compared the responses to .b between two groups of Japanese adolescents, ages 12–14 and 15–17 years. A total of 143 Japanese students, 74 in junior high (JH, ages 12–14) and 69 in senior high (SH, ages 15–17), participated in the 10-week .b. Participants completed questionnaires at baseline, post-intervention, and 2 months later. Measures included the Center for Epidemiologic Studies Depression Scale (CES-D), the Warwick–Edinburgh Mental Wellbeing Scale (WEMWBS), the Strengths and Difficulties Questionnaire (SDQ), and the Profile of Mood States, Second Edition (POMS2). The SH group showed significant improvements across all measures, while the JH group did not. The differences in the degree of improvement between the two groups were statistically significant or marginally significant. No worsening of depressive symptoms was observed in either group, including among younger or high-risk subgroups. These findings suggest that the response to .b may vary depending on the developmental stage of the participants, which may help explain the differing results between the FS and MS in the UK.