Mindfulness meditation in the trial literature usually means a structured program, most often mindfulness-based stress reduction, eight weeks of taught practice in sustained attention to the present moment. Apps and shorter courses borrow its name and its evidence.

The claims range from stress relief to cures, and the trials cover a narrower band. This guide reports what the better-designed trials, the ones with active control groups rather than waiting lists, actually found, because a waiting-list comparison measures the benefit of being given anything at all.

Proposed mechanisms include improved attention regulation, reduced rumination, a changed relationship to negative thoughts and sensations, and down-regulation of the stress response. Physiologically, meta-analyses of practices including mindfulness find lower cortisol, lower blood pressure and lower resting heart rate compared with active controls, though the interventions pooled are heterogeneous. Brain imaging studies report changes in attention and emotion networks; what they mean for symptoms is less clear than the imaging makes it look.

Against active controls: small to moderate. The 2014 JAMA Internal Medicine review of 47 trials in 3,515 people, restricted to trials with active controls, found moderate evidence that mindfulness programs improved anxiety, depression and pain, with effect sizes around 0.3 at eight weeks and somewhat smaller at three to six months, low evidence for stress and quality of life, and no evidence that meditation beat any active treatment, including drugs, exercise or other therapies.

In psychiatric disorders. A 2018 meta-analysis of 142 samples in 12,005 people found mindfulness-based interventions superior to no treatment, minimal treatment and non-specific active controls, slightly superior to specific active controls, and no different from evidence-based treatments at the end of treatment or at follow-up. The clearest support was for depression, pain, smoking and addiction.

In healthy people. A 2015 meta-analysis of 29 studies in 2,668 healthy adults found mindfulness-based stress reduction moderately effective, with large effects on stress, moderate effects on anxiety, depression and quality of life, maintained at an average of 19 weeks.

Physiology. A 2017 meta-analysis of 42 trials of yoga and mindfulness programs against active controls found lower evening and waking cortisol, lower ambulatory blood pressure, lower resting heart rate and lower fasting glucose, with heterogeneous interventions.

Meditation is generally safe, and the trials report few adverse events, partly because few looked. Case reports and more recent surveys describe adverse experiences in a minority of practitioners, including anxiety, depersonalisation and, rarely, psychosis, concentrated in intensive retreat practice and in people with a history of trauma or psychosis. Structured programs with trained teachers screen for that. An app does not.

Not a product, though apps and courses are, and they are sold without regulatory review of their claims. Mindfulness-based cognitive therapy is recommended in UK clinical guidelines for preventing recurrent depression, the one place a regulator-adjacent body has endorsed a specific mindfulness program for a specific condition.