Acceptance skills added nothing to mindfulness training in a trial of 392 people

Almost every definition of mindfulness has two halves. Pay attention to what is happening right now, and do it without judging what you find.

The second half is the harder one to pin down, and the one that carries most of the theory. A trial in the Journal of Clinical Psychology took it out to see what would happen.

Nothing happened. The group taught to notice and accept did no better than the group taught only to notice: no significant differences between them were observed for any outcome.

The two ingredients

The standard description of the practice contains both parts. Mindfulness involves maintaining attention or awareness on the present moment without making judgments.

Split that sentence and you have the trial. Maintaining attention is monitoring. Without making judgments is acceptance.

Meditation is the broader family it sits in. The term meditation refers to a variety of practices that focus on mind and body integration and are used to calm the mind and enhance overall well-being.

Real-world programs bundle a great deal together. Mindfulness-based stress reduction is a program that teaches mindful meditation, but it also includes discussion sessions and other strategies to help people apply what they have learned to stressful experiences.

That bundling is exactly why a dismantling trial is useful. If a program contains six things and works, you still do not know which of the six mattered.

Why anyone suspected acceptance was doing the work

The theory under test gives acceptance a specific job. Monitoring alone sharpens awareness of whatever is there, which for someone having a bad week means sharper awareness of a bad week. Acceptance is supposed to be what stops that becoming distressing.

On that account, monitoring without acceptance should be neutral at best and unpleasant at worst.

It has not worked out that way in testing. The researchers open by noting that previous studies based on the Monitoring and Acceptance Theory failed to find differential effects of monitoring plus acceptance and monitoring only training on negative affect.

Their move was to look somewhere else, investigating the differences from the perspective of mindfulness and emotional outcomes rather than negative mood alone.

How the trial worked

A total of 392 participants were randomly assigned to three groups: monitoring plus acceptance, monitoring only, or a waiting list.

The training was brief and delivered online. Participants received a 14-day online mindfulness training focused on monitoring and acceptance skills, or only monitoring skills, respectively.

Outcomes were assessed before the intervention, after the intervention, and at the 2-week follow up, using three standard questionnaires: one for mindfulness, one for positive and negative mood, and one for how strongly and how long a person reacts emotionally.

What the trial found

Both trainings worked against doing nothing. Both groups demonstrated significant improvements in the total mindfulness score and positive affect compared to the waiting-list group.

And the comparison the trial existed to make came out flat. No significant differences between the two training groups were observed for any outcome.

Not on mindfulness scores, not on positive mood, not on emotional reactivity. The authors’ summary is that the two had equivalent effects on mindfulness and emotional outcomes following a 2-week online training program.

Why “equivalent” is a stronger word than the result supports

This is the one place the paper reaches slightly past its data, and the distinction is worth carrying into other studies.

Finding no significant difference is not the same as showing two things are the same. A trial can only claim equivalence if it was designed to, with a margin agreed in advance defining how small a difference would count as “no real difference”, and enough people to rule out anything larger.

Nothing in the abstract describes that design. With about 130 people per group, a modest advantage for acceptance training could be real and still slip through undetected.

The honest version of this result is narrower and still interesting: across a 14-day online course, adding acceptance instruction produced no detectable benefit over attention instruction alone.

The other control problem

The comparison group waited. That tells you both trainings beat nothing, which was never really in doubt for self-reported measures.

What a waiting list cannot do is separate the training from the experience of being trained: the daily routine, the sense of doing something about your wellbeing, the expectation that it will help. An active control, something equally structured and equally plausible but without the mindfulness content, is what settles that.

So the trial’s internal comparison, acceptance against monitoring, is the strong part, because both those groups had the same amount of everything except the ingredient being tested. The comparison against the waiting list is the weak part, and it is the one that produced the positive findings.

What this cannot settle

Fourteen days is a short course, and the follow-up is two weeks. Long-term practice is a different thing from a fortnight of app sessions, and this design says nothing about it.

Everything was self-reported, including mindfulness itself. Asking people who have just been taught to be mindful whether they are being mindful is a measurement with a known lean to it.

The participants were volunteers for an online study rather than people seeking treatment, so this is not evidence about mindfulness for a diagnosed condition.

The paper is paywalled, so the authors’ own limitations section was not available for this piece.

What to take from it if you meditate

Not that acceptance is pointless. A brief online course is a weak test of a skill that traditionally takes months, and the finding is an absence of evidence over 14 days rather than evidence of absence.

What it does suggest is that the simple part of the practice may be carrying more of the benefit than the elaborate part. If you have bounced off mindfulness because the non-judging framing felt slippery or faintly mystical, the plain version, notice what is happening, appears to do about as much over two weeks.

One thing worth knowing regardless. Meditation and mindfulness practices usually are considered to have few risks, but few studies have examined these practices for potentially harmful effects, so it isn’t possible to make definite statements about safety. A 2020 review of 83 studies found that about 8 percent of participants had a negative effect from practicing meditation, most commonly anxiety and depression. That is a rate similar to psychological therapies generally, and it is not zero.

Anxiety is a feeling of fear, dread, and uneasiness, and if a practice sold as calming is producing it, that is a reason to stop and ask someone, not to push through.