Mindfulness effects on stress beyond placebo effects

Understanding how mindfulness really works is a requirement for its optimal application to reduce stress and suffering. It has been suggested that mindfulness' effects might be attributed to placebo effects. Yet, it has been difficult to disentangle how the different elements of a mindfulness-based intervention contribute to stress relief in regular RCTs. To this end, we propose a rigorous examination of a putative core element of mindfulness (i.e. decentering, the insight that experiences are impermanent) and of placebo effects (i.e. positive treatment expectancies). These elements will be manipulated in a balanced placebo design. This allows for better understanding the potential additive or interactive effects of the elements of mindfulness-based interventions on stress relief. This research provides a better understanding of how mindfulness might work, and will thus inform on future research methods and on methods for optimizing mindfulness effects.

With this study we aim to disentangle mindfulness and placebo effects on stress. We investigate how decentering (a core active component of mindfulness) and positive treatment expectations (a core component of placebo effects) interactively contribute to pain relief. We do so using a balanced-placebo design, i.e., a 2 x 2 factorial between-participants design, in which participants receive either a mindful decentering or sham decentering treatment which is introduced as being either an effective or a sham treatment. At baseline and post-intervention stress will be assessed.

In our primary analysis, we will examine if the mindful decentering and positive treatment expectations manipulations additively or interactively affect stress. The latter would suggest, depending on the direction of the interaction, that the combination of mindful decentering and positive treatment expectations is either more - or less - effective than the summed effect.
Additional exploratory hypotheses are detailed in the analysis plan (OSF url https://osf.io/mpzjk and doi: 10.17605/OSF.IO/MPZJK)

Participants take part in one session of an online experiment. The primary outcome is assessed once post-intervention.

To prevent floor effects, we will bring current stress to mind prior to the intervention by letting all participants read a short recent newspaper article regarding the corona crisis, asking them to briefly write about what worries them, and asking them to rate how worried they are about their health, financial, and social situation.

Expectation induction
Participants in the effective treatment expectations groups will be told that the training they will receive is a widely used training known to be very effective for stress relief. Participants in the sham treatment expectations group will be told that the training is a widely used sham training known to not affect stress.

Decentering induction
In the mindful decentering group, participants will listen to a short audiotape, with at its basis the insight that any thought or sensation arises and then dissipates again. Thus, that any such experience can be observed as a transient event. On the surface, the sham decentering instruction seems similar to the mindful decentering induction, but it is different in terms of content. Participants will listen to a short audiotape. A similar structure, wording, and calmness is given to this induction. Importantly, however, this induction does not include the key insight that experiences are impermanent events that can be observed as they arise and dissipate.