Trials of mindfulness to improve mental health selectively report positive results.

Researchers at McGill University in Montreal, Canada, analysed 124 published trials of mindfulness as a mental-health treatment, and found that scientists reported positive findings 60% more often than is statistically likely. The team also examined another 21 trials that were registered with databases such as ClinicalTrials.gov; of these, 62% were unpublished 30 months after they finished. The findings — reported in PLoS ONE on 8 April1 — hint that negative results are going unpublished.

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For the 124 trials, the researchers calculated the probability that a trial with that sample size could detect the result reported. Experiments with smaller sample sizes are more affected by chance and thus worse at detecting statistically significant positive results. The scientists’ calculations suggested that 66 of 124 trials would have positive results. Instead, 108 trials had positive results. And none of the 21 registered trials adequately specified which of the variables they tracked would be the main one used to evaluate success.

This doesn’t necessarily suggest that none of the mindfulness treatments work, says study co-author Brett Thombs, a psychologist at McGill and at the Jewish General Hospital in Montreal. “I have no doubt that mindfulness helps a lot of people,” he says. “I’m not against mindfulness. I think that we need to have honestly and completely reported evidence to figure out for whom it works and how much.”

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The bias towards reporting positive results is pervasive across many types of mental health, psychology and medical research, says Ferguson. For example, the widely popularized theory of ego depletion — that people have limited self-control for decisions — recently failed to hold up in a large replication trial. “A lot of these things are reported to be true, they’re in a TEDx talk,” he says. “Now we're seeing, when we look at things much more closely, we’ve kind of been bullshitting people [for] a decade.”

...http://www.nature.com/news/power-of-positive-thinking-skews-mindfulness-studies-1.19776