Probably the most thorough and up to date review of meditation research was published in 2007 by a team led by Ospina, specifically contracted by the US Department of Health and Human Services to assess the evidence base. They included both randomised and non-randomised trials. In their assessment of more than 800 studies they concluded:
“Many uncertainties surround the practice of meditation. Scientific research on meditation practices does not appear to have a common theoretical perspective and is characterised by poor methodological quality. Firm conclusions on the effects of meditation in healthcare cannot be drawn based on the available evidence.”
Ospina’s review represented a massive effort by a large team of researchers. Its thorough and comprehensive nature ensures that its contribution to the field of meditation research will be of great value. There are a number of features in the review’s design however that would seem to prevent important questions about specific effects and related issues from being clearly answered, such as:
- The inclusion of a wide variety of comparative studies, not just randomised controlled trials.
- Techniques that may not be widely accepted as meditation, such as Yoga, Tai Chi and Qigong. These practices include meditation as a component of their practice but also include many other practices such as physical exercise, dietary modification and other lifestyle choices whose confounding and non-specific effects are difficult to separate from any effects of meditation.
- Effect size calculations did not seem to take into account the heterogeneity of control groups and their widely varying ability to confound outcomes since the control methods themselves elicit both non-specific and, in some cases, specific effects.