Key messages
· We looked primarily at two main types of meditation, mindfulness-based interventions (MBIs) and transcendental meditation (TM), compared to receiving something else or nothing else (referred to as active and inactive comparison groups, respectively). We found inconsistent results for many of the outcomes of interest.
· Compared to inactive comparators, MBIs probably reduce stress, and may also reduce anxiety and depression and blood pressure. TM may reduce blood pressure when compared to either active or inactive comparators, with few studies reporting psychological outcomes. Results will be more certain with the addition of further well-conducted studies.
What is cardiovascular disease?
Cardiovascular disease (CVD) includes several different diseases of the heart and blood vessels, some of which are caused by problems like high cholesterol, physical inactivity, stress, poor diet, being overweight, smoking, or drinking alcohol. Overall, CVDs are the world’s leading cause of death.
How can meditation help?
Meditation may help to reduce people’s stress levels, which could benefit them directly (for example, by lowering blood pressure), and indirectly by helping them to avoid unhealthy ways of coping with stress (for example, smoking, drinking alcohol, or making poor food choices).
What types of meditation did we look at?
We looked at two main types of meditation for this study:
· mindfulness-based interventions (MBI);
· transcendental meditation (TM).
What did we want to find out?
We wanted to find out if meditation helped to:
· reduce the risk of CVD clinical events, such as death, heart attack, stroke, or chest pain;
· reduce blood pressure;
· improve stress, depression, anxiety, and well-being;
· improve blood measures like cholesterol and blood glucose levels;
· reduce weight;
· reduce smoking;
· improve quality of life and people’s ability to cope.
What did we do?
We searched for studies that looked at meditation compared with no intervention (inactive comparators) or another non-pharmacological intervention (active comparators), in people at high risk of developing CVD and people who already had established CVD. We assessed outcomes for the totality of the participants and separately for these two groups.
We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found 81 studies that involved 6971 people either at high risk of or who already had CVD. The studies lasted between 12 weeks and five years.
Only one MBI study and one TM study reported CVD clinical events, and we found that either type of meditation may have little to no effect, but we are very uncertain about the results.
Six studies (388 people) that compared MBIs to active comparators suggest that it may have little to no effect on blood pressure, but we are uncertain about the results. Results from eight studies (774 people) found that TM probably reduces systolic blood pressure compared to active comparators, but the evidence for diastolic blood pressure was less certain.
When compared to inactive comparators, people who practised mindfulness (nine studies, 379 people) may have reductions in blood pressure, but results were inconsistent. When comparing TM to inactive comparators (2 studies, 154 people) we found that TM may reduce blood pressure.
We found that there was probably little or no difference in anxiety, depression, or well-being between MBIs and active comparators. Six studies (357 people) reported that stress probably improved more in people who practised mindfulness. Five studies (421 people) reported little to no effect on depression among people who practised TM compared with another intervention. We are very uncertain about the effect of TM on anxiety or stress.
When compared to inactive comparators, people who practised mindfulness may have reductions in anxiety (nine studies, 533 people), depression (15 studies, 912 people), and stress (11 studies, 708 people), but results were inconsistent. Two trials (198 people) reported a probable increase in well-being among people who practised mindfulness, compared to no intervention. We found no differences in the results for blood pressure, anxiety, depression, and stress, where we had enough studies to compare people at risk of CVD with those with established CVD.
One small study reported two unwanted/adverse effects of MBI when compared to inactive comparators. One participant had transitory vertigo during head rolling in mindful movement and in another the MBI caused resurfacing of repressed traumatic memories and depression. This participant received counselling and continued with MBI, which they found beneficial.
What are the limitations of the evidence?
Even though we tried to group studies by the type of meditation intervention and by comparison groups, so they were more similar for the analyses, there was still a lot of inconsistency in the findings that remains unexplained.
Most of the studies were small in size, and we are uncertain as to how well they were carried out, mainly due to poor reporting.
The search cut-off date of November 2021 is a limitation of the review. However, in May 2023 we revisited the status of the 74 ongoing studies and provided details of these. Nine studies were found to have been completed in this time and will be formally assessed in an update of this review.
How up-to-date is this evidence?
The evidence is up-to-date to November 2021.
Despite the large number of studies included in the review, heterogeneity was substantial for many of the outcomes, which reduced the certainty of our findings. We attempted to address this by presenting four main comparisons of MBIs or TM versus active or inactive comparators, and by subgroup analyses according to primary or secondary prevention, where there were sufficient studies. The majority of studies were small and there was unclear risk of bias for most domains. Overall, we found very little information on the effects of meditation on CVD clinical endpoints, and limited information on blood pressure and psychological outcomes, for people at risk of or with established CVD.
This is a very active area of research as shown by the large number of ongoing studies, with some having been completed at the time of writing this review. The status of all ongoing studies will be formally assessed and incorporated in further updates.
Interventions incorporating meditation to address stress, anxiety, and depression, and improve self-management, are becoming popular for many health conditions. Stress is a risk factor for cardiovascular disease (CVD) and clusters with other modifiable behavioural risk factors, such as smoking. Meditation may therefore be a useful CVD prevention strategy.
To determine the effectiveness of meditation, primarily mindfulness-based interventions (MBIs) and transcendental meditation (TM), for the primary and secondary prevention of CVD.
We searched CENTRAL, MEDLINE, Embase, three other databases, and two trials registers on 14 November 2021, together with reference checking, citation searching, and contact with study authors to identify additional studies.
We included randomised controlled trials (RCTs) of 12 weeks or more in adults at high risk of CVD and those with established CVD. We explored four comparisons: MBIs versus active comparators (alternative interventions); MBIs versus non-active comparators (no intervention, wait list, usual care); TM versus active comparators; TM versus non-active comparators.
We used standard Cochrane methods. Our primary outcomes were CVD clinical events (e.g. cardiovascular mortality), blood pressure, measures of psychological distress and well-being, and adverse events. Secondary outcomes included other CVD risk factors (e.g. blood lipid levels), quality of life, and coping abilities. We used GRADE to assess the certainty of evidence.
We included 81 RCTs (6971 participants), with most studies at unclear risk of bias.
MBIs versus active comparators (29 RCTs, 2883 participants)
Systolic (SBP) and diastolic (DBP) blood pressure were reported in six trials (388 participants) where heterogeneity was considerable (SBP: MD -6.08 mmHg, 95% CI -12.79 to 0.63, I2 = 88%; DBP: MD -5.18 mmHg, 95% CI -10.65 to 0.29, I2 = 91%; both outcomes based on low-certainty evidence). There was little or no effect of MBIs on anxiety (SMD -0.06 units, 95% CI -0.25 to 0.13; I2 = 0%; 9 trials, 438 participants; moderate-certainty evidence), or depression (SMD 0.08 units, 95% CI -0.08 to 0.24; I2 = 0%; 11 trials, 595 participants; moderate-certainty evidence). Perceived stress was reduced with MBIs (SMD -0.24 units, 95% CI -0.45 to -0.03; I2 = 0%; P = 0.03; 6 trials, 357 participants; moderate-certainty evidence). There was little to no effect on well-being (SMD -0.18 units, 95% CI -0.67 to 0.32; 1 trial, 63 participants; low-certainty evidence). There was little to no effect on smoking cessation (RR 1.45, 95% CI 0.78 to 2.68; I2 = 79%; 6 trials, 1087 participants; low-certainty evidence). None of the trials reported CVD clinical events or adverse events.
MBIs versus non-active comparators (38 RCTs, 2905 participants)
Clinical events were reported in one trial (110 participants), providing very low-certainty evidence (RR 0.94, 95% CI 0.37 to 2.42). SBP and DBP were reduced in nine trials (379 participants) but heterogeneity was substantial (SBP: MD -6.62 mmHg, 95% CI -13.15 to -0.1, I2 = 87%; DBP: MD -3.35 mmHg, 95% CI -5.86 to -0.85, I2 = 61%; both outcomes based on low-certainty evidence). There was low-certainty evidence of reductions in anxiety (SMD -0.78 units, 95% CI -1.09 to -0.41; I2 = 61%; 9 trials, 533 participants; low-certainty evidence), depression (SMD -0.66 units, 95% CI -0.91 to -0.41; I2 = 67%; 15 trials, 912 participants; low-certainty evidence) and perceived stress (SMD -0.59 units, 95% CI -0.89 to -0.29; I2 = 70%; 11 trials, 708 participants; low-certainty evidence) but heterogeneity was substantial. Well-being increased (SMD 0.5 units, 95% CI 0.09 to 0.91; I2 = 47%; 2 trials, 198 participants; moderate-certainty evidence). There was little to no effect on smoking cessation (RR 1.36, 95% CI 0.86 to 2.13; I2 = 0%; 2 trials, 453 participants; low-certainty evidence). One small study (18 participants) reported two adverse events in the MBI group, which were not regarded as serious by the study investigators (RR 5.0, 95% CI 0.27 to 91.52; low-certainty evidence).
No subgroup effects were seen for SBP, DBP, anxiety, depression, or perceived stress by primary and secondary prevention.
TM versus active comparators (8 RCTs, 830 participants)
Clinical events were reported in one trial (201 participants) based on low-certainty evidence (RR 0.91, 95% CI 0.56 to 1.49). SBP was reduced (MD -2.33 mmHg, 95% CI -3.99 to -0.68; I2 = 2%; 8 trials, 774 participants; moderate-certainty evidence), with an uncertain effect on DBP (MD -1.15 mmHg, 95% CI -2.85 to 0.55; I2 = 53%; low-certainty evidence). There was little or no effect on anxiety (SMD 0.06 units, 95% CI -0.22 to 0.33; I2 = 0%; 3 trials, 200 participants; low-certainty evidence), depression (SMD -0.12 units, 95% CI -0.31 to 0.07; I2 = 0%; 5 trials, 421 participants; moderate-certainty evidence), or perceived stress (SMD 0.04 units, 95% CI -0.49 to 0.57; I2 = 70%; 3 trials, 194 participants; very low-certainty evidence). None of the trials reported adverse events or smoking rates.
No subgroup effects were seen for SBP or DBP by primary and secondary prevention.
TM versus non-active comparators (2 RCTs, 186 participants)
Two trials (139 participants) reported blood pressure, where reductions were seen in SBP (MD -6.34 mmHg, 95% CI -9.86 to -2.81; I2 = 0%; low-certainty evidence) and DBP (MD -5.13 mmHg, 95% CI -9.07 to -1.19; I2 = 18%; very low-certainty evidence). One trial (112 participants) reported anxiety and depression and found reductions in both (anxiety SMD -0.71 units, 95% CI -1.09 to -0.32; depression SMD -0.48 units, 95% CI -0.86 to -0.11; low-certainty evidence). None of the trials reported CVD clinical events, adverse events, or smoking rates.