Mindfulness meditation can help ease anxiety, depression and pain, but scientists found little evidence that meditation helped other conditions including substance abuse or sleep and attention problems.
The scientists, reporting Monday in the Journal of the American Medical Assn. Internal Medicine, noted that many Americans had turned to mindfulness or transcendental meditation to improve their lives and to cope with medical and other problems. But there's little clarity, they said, among healthcare providers about the value of these alternatives to standard medical care.
The scienctists said they measured the effect on depression, for example, as what would be expected using an antidepressant.
Meditation has taken hold in corporate offices, schools and community groups around the United States in recent years. Some universities have established meditation programs or centers in which to study it.
Dr. Madhav Goyal of Johns Hopkins University and colleagues reviewed 47 randomized clinical trials, with a total of 3,515 people, for evidence of the effects of meditation. They wrote that doctors need to be able to talk with their patients about the role meditation might play in efforts to address stress.
But, they also said, "Stronger study designs are needed."
They found low evidence or no effect or insufficient evidence to draw conclusions about meditation and attention, substance use, eating habits, sleep and weight. They found no evidence that meditation worked better than exercise or drugs.
The researchers noted that meditation programs vary in many ways, making them difficult to assess. The clinical trials they reviewed lasted from three weeks to more than five years. Some studied psychiatric populations. Others focused on smokers and alcoholics, and still others on people with various diseases.
Meditation and many other alternative therapies have little evidence to demonstrate their effectiveness, Dr. Allan Goroll of Harvard Medical School said in a commentary accompanying the report.
"The relative scarcity of scientifically derived data on efficacy and safety stems from a number of factors, ranging from a lack of financial incentives for practitioners and suppliers (Why study something that is already profitable and accepted by patients?) to difficulty measuring outcomes," he wrote.
The researchers also noted that one strength of their study was that it was limited to randomized clinical trials, "which should give clinicians greater confidence" in the reported benefits. No harm was reported from meditation programs.
Susan Smalley, founding director of the Mindful Awareness Research Center at UCLA, agreed with the authors that more study was needed.
"What works best for each individual differs, and factors such as cost, time, need for a trainer or clinician, make certain practices easier for some than others," she said in an email. "Since adherence - or sticking with the practice - is important, finding meditation (a free and easy-to-learn practice) effective for depression, anxiety, and pain, even if small or moderate in size, in this systematic investigation is promising."