Recently, there has been a flurry of research interest in mindfulness – one could almost call it hype! Not that this is reflected in loads of rigorous trials, rather it manifests itself by an unprecedented amount of systematic reviews on mindfulness being published.
I conducted a Medline search on 8/2/2022 for meta-analyses of mindfulness. It resulted in no less than 9 such papers. Here are their conclusions:
- This meta-analysis suggests that SOF is a moderately effective evidence-based practice for reducing disruptive behavior.
- In conclusion, both mindfulness interventions showed robust evidence on anxiety symptoms in pretest-posttest periods compared to control groups. Few studies and lack of evidence of follow-up periods were the main limitations found.
- Memory specificity did not significantly differ from baseline to post-treatment for either MBCT and Control interventions.
- Although this review was limited by search strategies and most of the included studies were of low quality, it still provided some tentative support for PSIs for the treatment of TOPFA women.
- Meta-regression results showed that some heterogeneity in effect size could be accounted for by intervention dosage, study population, and study design. Our findings quantify MBIs’ potential for improving immune function and thus impacting somatic disorders.
- Mindfulness interventions somewhat improved depression in emerging adults. Because primary researchers did not report the adverse effects, mindfulness interventions should be used with caution. Future researchers might study the adverse effects of mindfulness interventions as well as the long-term effects.
- The effect of MBIs on pain in cancer patients was demonstrated in our analysis, albeit with small effect sizes. High-quality RCTs are needed to verify the efficacy of MBIs on cancer patients or survivors with pain complaints. Future trials should take into account the specific pain outcome measures (pain intensity or pain interference), the approach of intervention provision (clinic-based or remote MBI, group or individual practice), the duration and frequency of interventions and the comparators (passive or active control arms).
- This meta-analysis found that MBIs had beneficial effects on mental health such as psychological distress and wellbeing in nurses.
- Because MBIs show promise across some PICOS, future RCTs and meta-analyses should build on identified strengths and limitations of this literature.
This amounts to about two systematic reviews/meta-analyses per week!
And what do these papers tell us?
If you are an advocate of mindfulness, you probably conclude that your pet therapy is supported by reasonably sound evidence. If, however, you think a little more critically, you would probably see that the evidence is far from strong. The effect size is usually small and of doubtful clinical relevance. This is, I think, important because clinical trials of mindfulness cannot easily control for placebo effects (there is no adequate placebo that would allow patients to be blinded). Therefore, the small effects that do emerge in systematic reviews/meta-analyses are most likely the result of a placebo response and not due to mindfulness per se.
My conclusion is therefore not nearly as positive as that of fans of mindfulness: the collective evidence suggests to me that the success of mindfulness relies mostly or even entirely on the placebo effect. And this means that even dozens of further systematic reviews are not going to advance our knowledge significantly. What is needed, I think, is a few truly rigorous studies aimed at determining whether the effects of mindfulness are specific or non-specific in nature. My prediction is that, once we have this evidence, the current hype around mindfulness will calm down.