This project aims to investigate how individual differences influence the effects of mindfulness meditation to gain a first understanding of the personalised effects of mindfulness and uncover for whom mindfulness is beneficial and for whom it may be harmful. In a first step towards a better understanding of the effects of mindfulness mediation on each individual, the investigators aim to identify the mechanisms underlying the effects of mindfulness meditation on mental health and wellbeing (first objective). Based on prior research, the investigators hypothesise that mindfulness meditation exerts its effects via internal awareness, decentering, and non-judgment, but the investigators will also explore other mindfulness skills as potential mechanisms. Knowing the underlying mechanisms will help understand why mindfulness meditation leads to improved mental health in some individuals while it may lead to harm in other individuals. In a second step, the investigators aim to examine specific characteristics of individuals that may influence whether mindfulness meditation has beneficial or possibly harmful effects. Specifically, the investigators aim to examine how three candidate factors, namely trauma symptoms, tendency to dissociate, and repetitive negative thinking, influence the effect of mindfulness meditation on mental health and wellbeing (second objective). Knowing how these individual characteristics influence the effect of mindfulness meditation will clarify for whom mindfulness works best and for whom it may lead to undesired effects.~For both objectives, mental health and wellbeing will be measured using self-report questionnaires to determine the effects of the mindfulness intervention on participants' mental health and wellbeing. To achieve the first objective, the investigators will measure change of different mindfulness skills (the hypothesised mechanisms) with self-report questionnaires across the mindfulness intervention in order to test whether the mindfulness intervention leads to change in mindfulness skills, which in turn leads to change in outcomes. To achieve the second objective, the investigators will measure baseline levels of candidate factors with self-report questionnaires in order to test whether these candidate factors influence in what way the mindfulness intervention affects mental health and wellbeing. Candidate factors are trauma history and symptoms, tendency to dissociate, and repetitive negative thinking. Additionally, the investigators will measure obsessive-compulsive disorder related beliefs as potential candidate factors, as these beliefs influenced the effects of mindfulness in our own clinical practice. Meditation practice-related variables such as frequency, intentions and previous experience will be measured in order to control for potential practice-related effects on mental health.
The overall aim of this observational study is to investigate how individual differences influence the effects of mindfulness meditation to uncover for whom mindfulness is beneficial and for whom it may be harmful. The first objective is to identify the mechanisms underlying the effects of mindfulness meditation on mental health. The second objective is to examine how three candidate factors, namely trauma symptoms, tendency to dissociate, and repetitive negative thinking, influence the effect of mindfulness meditation on mental health.~Adults who enrolled for a Mindfulness-Based Intervention (MBI) at the participating sites (n=120 for each site) will be invited to participate. Before the start of the MBI, after half of the sessions, at the end of the MBI and at 3-months follow-up, participants will complete self-report questionnaires. The main outcomes are symptoms of anxiety and depression, quality of life, wellbeing, and adverse effects resulting from the MBI. A subset of participants will be invited for a semi-structured interview after the end of the intervention.