Abstract
BACKGROUND: Mindfulness‑based interventions (MBIs) are widely adopted to mitigate workplace stress, yet their month-by-month impact on mood has rarely been quantified. METHODOLOGY: A total of 25 full‑time Japanese employees (60% men; mean ± SD age 40.1 ± 6.2 years) were randomised to a three‑month MBI arm (n = 12) or a wait‑list control arm (n = 13). The MBI comprised three 90‑min workshops (Weeks 0, 4, 8) plus 10‑min daily self‑practice. Measuring Total Mood Disturbance scores (TMD; POMS‑2‑SF) was the primary outcome; fatigue (100‑mm VAS) and presenteeism (Stanford Presenteeism Questionnaire; SPQ) were secondary. Assessments occurred at baseline and monthly for three months. Linear mixed‑effects models with participant random intercepts tested group × time interactions; 95% bootstrap CIs (1,000 iterations) were generated. RESULTS: TMD declined cumulatively in the MBI arm (‑4.2, ‑4.4, ‑6.3 points at Months 1‑3), while controls rose +1.0 point; interaction β = ‑2.56 points·month⁻¹ (95 % CI ‑4.31 to ‑0.71, p = 0.014). Fatigue (p = 0.47) and presenteeism (p = 0.41) trends favoured the intervention but were non‑significant. CONCLUSIONS: A low‑dose workplace MBI produced additive three‑month reductions in mood disturbance. Monthly assessments clarify change dynamics and justify larger confirmatory trials integrating physiological and organisational endpoints.