Zen meditation: an integration of current evidence.

OBJECTIVE: Despite the growing interest in the neurobiological and clinical correlates of many meditative practices, in particular mindfulness meditations, no review has specifically focused on current evidence on electroencephalographic, neuroimaging, biological, and clinical evidence about an important traditional practice, Zen meditation.
METHODS: A literature search was conducted using MEDLINE, the ISI Web of Knowledge, the Cochrane collaboration database, and references of selected articles. Randomized controlled and cross-sectional studies with controls published in English prior to May 2008 were included.
RESULTS: Electroencephalographic studies on Zen meditation found increased alpha and theta activity, generally related to relaxation, in many brain regions, including the frontal cortex. Theta activity in particular seemed to be related to the degree of experience, being greater in expert practitioners and advanced masters. Moreover, Zen meditation practice could protect from cognitive decline usually associated with age and enhance antioxidant activity. From a clinical point of view, Zen meditation was found to reduce stress and blood pressure, and be efficacious for a variety of conditions, as suggested by positive findings in therapists and musicians.
CONCLUSION: To date, actual evidence about Zen meditation is scarce and highlights the necessity of further investigations. Comparison with further active treatments, explanation of possible mechanisms of action, and the limitations of current evidence are discussed.