Louise Hartley, Angelique Mavrodaris, Nadine Flowers, Edzard Ernst, Karen Rees

A major determinant in cardiovascular disease (CVD) is stress. As transcendental meditation (TM) is thought to help in lowering negative stress indicators, it may be a beneficial strategy for the primary prevention of CVD. To determine the effectiveness of TM for the primary prevention of CVD. We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 10); MEDLINE (Ovid) (1946 to week three November 2013); EMBASE Classic and EMBASE (Ovid) (1947 to week 48 2013); ISI Web of Science (1970 to 28 November 2013); and Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment Database and Health Economics Evaluations Database (November 2013). We also searched the Allied and complementary Medicine Database (AMED) (inception to January 2014) and IndMed (inception to January 2014). We handsearched trial registers and reference lists of reviews and articles and contacted experts in the field. We applied no language restrictions. We included randomised controlled trials (RCTs) of at least three months' duration involving healthy adults or adults at high risk of CVD. Trials examined TM only and the comparison group was no intervention or minimal intervention. We excluded trials that involved multi-factorial interventions. Outcomes of interest were clinical CVD events (cardiovascular mortality, all-cause mortality and non-fatal events) and major CVD risk factors (e.g. blood pressure and blood lipids, occurrence of type 2 diabetes, quality of life, adverse events and costs). Two authors independently selected trials for inclusion, extracted data and assessed the risk of bias. We identified four trials (four papers) (430 participants) for inclusion in this review. We identified no ongoing studies. The included trials were small, short term (three months) and at risk of bias. In all studies, TM was practised for 15 to 20 minutes twice a day.None of the included studies reported all-cause mortality, cardiovascular mortality or non-fatal endpoints as trials were short term, but one study reported survival rate three years after the trial was completed. In view of the considerable statistical heterogeneity between the results of the studies for the only outcomes reported, systolic blood pressure (I(2) = 72%) and diastolic blood pressure (I(2) = 66%), we decided not to undertake a meta-analysis. None of the four trials reported blood lipids, occurrence of type 2 diabetes, adverse events, costs or quality of life. Currently, there are few trials with limited outcomes examining the effectiveness of TM for the primary prevention of CVD. Due to the limited evidence to date, we could draw no conclusions as to the effectiveness of TM for the primary prevention of CVD. There was considerable heterogeneity between trials and the included studies were small, short term and at overall serious risk of bias. More and larger long-term, high-quality trials are needed.