 Mindfulness is now a billion-dollar industry, with as many as one in five Fortune 500 companies implementing some kind of workplace mindfulness programs. It has been rebranded from hippie-to-be-nonsense to portrayals such as brain training, said to sell it better. These reductionist commodified forms have been derided as mic-mindfulness, who cares what they call it if it works, but does it? Research into mindfulness has been complicated by the fact that the term can mean anything from informal practices such as conscious awareness while eating to structured meditation programs involving designated specific times to sit in a specific posture or attending to your breathing, for example. This has made an understanding of the efficacy hard to capture. Can't hurt, though, right? Well, there have been more than 20 observational studies or case reports documenting instances of adverse effects, such as meditation-induced psychosis, mania, anxiety, panic. In one perspective, study of an intensive meditation retreats 60% reported to at least one adverse effect, including one individual who was hospitalized for a psychotic break. Even outside of an immersive retreat environment, as many as 12% of meditators recall serious negative side effects within 10 days of initiating the practice. It's considered plausible that adverse effects occur at rates approximating that of psychotherapy, with about one in 20 reporting lasting negative effects of psychological treatment. With about 18 million Americans practicing meditation, and as many as a million new meditators a year, even a 5% adverse event rate could mean hundreds of thousands of negative side effects a year. As with any medical intervention, though, it's all about risks versus benefits. Unfortunately, many of the benefits appear to have been overstated. This commentary in the Journal of the American Psychological Association notes that even the books on mindfulness written by scientists are bursting with magical promises of peace, happiness, and well-being. Contrary to the popular perception, the evidence for even the most well-founded benefits are not entirely conclusive. This is not an issue unique to meditation, of course. There's a replication crisis across the entire field of experimental psychology, where many of the landmark findings in the social sciences published in even the most prestigious journals don't appear to be reproducible. Drug companies aren't the only ones to suppress the publication of studies that don't come out the way they wanted. The majority of mindfulness-based trials apparently never see the light of day, raising the specter of a similar publication bias. Presumably if the study showed promising results, they would have been released rather than shelved. And even many of the ones that do make it into the scientific record are underwhelming. The Federal Agency for Healthcare Research and Quality published a systematic review of the available data and concluded that mindfulness meditation worked best for improving anxiety, depression, and pain, but even then the quality of evidence was only moderate. What about weight loss? Mindfulness-based modalities can help with stress management, self-control, and decreased impulsive eating, as well as binge eating and emotional eating, all of which might facilitate weight management. However, a systematic review of the evidence published about five years ago failed to find evidence of significant or consistent weight loss. Part of the problem is compliance. Like any other diet or lifestyle intervention, mindfulness only works if you do it. For example, randomize women to attend four to two-hour workshops that teach mindfulness techniques such as cognitive diffusion, and after six months they lost no more weight on average than the control group. However, if you exclude those who reported never applying the workshop principles at all and just look at those who at least used them some of the time, their weight loss did beat out the control group by about five pounds. Other studies have shown a lack of weight gain rather than loss. For example, this study found that obese subjects in the control group continued to gain weight at about a pound a month, whereas the weight of those in the mindfulness intervention group remained stable. Put all the studies together in the latest and largest review published did find mindfulness-based interventions could lead to weight loss compared to doing nothing, an average of about seven pounds over around four months. Pitted head to head, they didn't beat out other lifestyle change interventions, but the nice thing about stress management and mindfulness is that they can be practiced on top of whatever else you're doing.