Dose-Response Effects of Mindfulness Meditation

The study will compare the efficacy of receiving different "doses" of mindfulness training over a 28-day period in a prospective 4-armed, parallel-group randomised controlled trial. Participants will be randomised into one of the 4 groups: 10 minutes of meditation per day, 20 minutes of meditation per day, 30 minutes of meditation per day, or a minimal dose of 3-4 minutes of meditation per day. All participants will be encouraged not to complete any further mindfulness training or practice during the intervention period, apart from informal practice during daily life. Self-reported biopsychosocial measures will be evaluated at four time points; before randomization (baseline; T0), 2 weeks after randomisation (mid-intervention, T0.5), 4 weeks after randomization (post-intervention; T1), and 2 months after randomization (post follow-up; T2). In addition, weekly and daily outcomes will be evaluated between T0 and T1. Individual adherence and meditation-related experiences (including adverse events) will be monitored and compared across treatments. The trial will consist of three main phases: the Run-in Period, the Intervention Period, and the Follow-up period, as described below.