Research on meditation
|This article needs more medical references for verification or relies too heavily on primary sources. (April 2015)|
|This article possibly contains original research. (April 2015)|
Since the 1950s hundreds of studies on meditation have been conducted, though many of the early studies were flawed and thus yielded unreliable results. More recent reviews have pointed out many of these flaws with the hope of guiding current research into a more fruitful path.
Research on the processes and effects of meditation is a growing subfield of neurological research. Modern scientific techniques and instruments, such as fMRI and EEG, have been used to see what happens in the bodies of people when they meditate, and how their bodies and brains change after meditating regularly.
Meditation is a broad term which encompasses a number of practices that generally involve the direct modulation of awareness, attention, thought, and emotion that are intended to bring about positive changes in health, well being, and performance. Some reports assessed that further research should be directed towards the theoretical grounding, types and definition of meditation, and continued empirical observations by studying the effects of various types of meditations on human physiology and neurology.
- 1 Mindfulness
- 1.1 Meta-analyses
- 1.2 Singular studies
- 1.3 Mindfulness scales
- 1.4 Evidence of benefits of Mindfulness
- 1.5 Attention and Mindfulness
- 1.6 Emotion regulation and Mindfulness
- 1.7 Future directions
- 2 Research on other types of meditation
- 3 Research on unspecified or multiple types of meditation
- 4 Weaknesses in historic meditation research
- 5 See also
- 6 Notes
- 7 References
- 8 External links
A 2003 meta-analysis found that Mindfulness-Based Stress Reduction (MBSR) may be broadly useful for individuals attempting to cope with clinical and nonclinical problems. Diagnoses for which MBSR was found to be helpful included chronic pain, fibromyalgia, cancer patients and coronary artery disease. Improvements were noted for both physical and mental health measures.
In a 2014 meta-analysis of scientific studies on mindfulness meditation, the US Agency for Healthcare Research and Quality said that "Meditation programs, in particular mindfulness programs, reduce multiple negative dimensions of psychological stress".:vii In particular, the meta-analysis found "that there is moderate strength of evidence that mindfulness meditation programs are beneficial for reducing pain severity, and there is low to moderate strength of evidence that mindfulness meditation programs may lead to improvement in dimensions of negative affect, including anxiety, depression, and perceived stress/general distress.:130 The meta-analysis did not conclude that mindfulness meditation was more effective than other therapies "for any outcome" when compared to "therapies as exercise, yoga, progressive muscle relaxation, cognitive behavioral therapy, and medications.":ES-10; 131[note 1]
A 2013 metastudy of mindfulness meditation found moderately improved anxiety and depression. Another study showed higher mindfulness and reduced stress correlated with the number of days meditated per week.
A study published in the journal Cancer on November 3, 2014 investigated how various psychosocial interventions affected telomere length in breast cancer survivors, who had completed their cancer treatment at least three months prior to participating in the study. In total, 88 participants were split up and randomly placed into two intervention groups and one control group: mindfulness-based cancer recovery (MBCR), which included performing mindfulness meditation and Hatha yoga; supportive-expressive group therapy (SET), which included participating in group therapy sessions for expressing emotions and cultivating coping skills; and stress management seminar participation, which was the control group. While the MBCR group contained a psychosocial intervention and a physical activity intervention (i.e., yoga), the SET group only included a psychosocial intervention without any comparable physical activity intervention. There was statistically little difference on telomere length between the MBCR group and the SET group; however, both MBCR and SET were statistically more effective at preserving telomere length than the control group. It is currently unknown if yoga by itself, mindfulness meditation by itself, or yoga combined with mindfulness meditation was responsible for preserving telomere length in participants.
Another study found that a short program in MBSR produces demonstrable effects on the immunity.  Meditators had a rise in their antibody titers to influenza vaccine compared to non-meditators.
Some studies suggest that mindfulness meditation may significantly shape individuals’ personality toward a more coherent and healthy sense of self and identity, including aspects such as sense of responsibility, authenticity, compassion, self-acceptance and character.
In the relatively new field of western psychological mindfulness, researchers attempt to define and measure the results of mindfulness primarily through controlled, randomised studies of mindfulness intervention on various dependent variables. The participants in mindfulness interventions measure many of the outcomes of such interventions subjectively. For this reason, several mindfulness inventories or scales (a set of questions posed to a subject whose answers output the subject's aggregate answers in the form of a rating or category) have arisen. Twelve such methods are mentioned by the Mindfulness Research Guide[dead link] Examples include:
- the Mindful Attention Awareness Scale (MAAS);
- the Freiburg Mindfulness Inventory;
- the Kentucky Inventory of Mindfulness Skills;
- the Cognitive and Affective Mindfulness Scale.
Through the use of these scales - which can illuminate self-reported changes in levels of mindfulness, the measurement of other correlated inventories in fields such as subjective well-being, and the measurement of other correlated variables such as health and performance - researchers have produced studies that investigate the nature and effects of mindfulness. The research on the outcomes of mindfulness falls into two main categories: stress reduction and positive-state elevation.
Evidence of benefits of Mindfulness
A 2013 meta-analysis of mindfulness-based therapies (MBT), involving 209 studies and 12,145 participants, indicated that MBT is moderately effective in pre-post studies, superior to some treatments (psychoeducation, supportive therapy, relaxation, imagery, and art-therapy), but not more effective than traditional cognitive behavioral therapy. The analysis found that MBT was more effective in treating psychological disorders than it was in treating physical or medical conditions. MBT showed "large and clinically significant effects in treating anxiety and depression", with gains maintained at follow-up. These findings were similar to those obtained in previous meta-analyses. The authors acknowledged, however, the wide variation between the studies in their design, interventions, participants, outcomes, and quality; it is thus possible that their conclusions may be overstated.
A systematic study on the efficacy of various forms of meditation programs (including mantra, transcendental meditation, and mindfulness meditation), commissioned by the US Agency for Healthcare Research and Quality, was published in 2014. After a review of 17,801 citations, the study based its conclusions on 41 randomized controlled trials with an active control, involving 2,993 participants. It concluded that "Meditation programs, in particular mindfulness programs, reduce multiple negative dimensions of psychological stress.":vii The assessment found that:
- "Mindfulness meditation programs improved multiple dimensions of negative affect, including anxiety, depression, and perceived stress/general distress ... the effects were significant for anxiety and marginally significant for depression at the end of treatment, and these effects continued to be significant at 3-6 months for both anxiety and depression";:130
- there is a "small and consistent signal that any domain of negative affect is improved in mindfulness programs when compared with a nonspecific active control";:131
- although the effects were small, they are "fairly comparable with what would be expected from the use of an antidepressant in a primary care population";:131
- MBT "did not show superiority for any outcome" when compared to such therapies as exercise, yoga, progressive muscle relaxation, cognitive behavioral therapy, and medications;:131
- MBSR has a small effect on general pain severity, and causes "a statistically significant 30 percent reduction in abdominal pain severity at 2 months that maintained at six months".:133
- "no effect or insufficient evidence of any effect of meditation programs on positive mood, attention, substance use, eating habits, sleep, and weight." [note 2]
In 2011, National Center for Complementary and Alternative Medicine (NCCAM) released findings from a study in which magnetic resonance images were taken of the brains of 16 participants 2 weeks before and after the participants joined the mindfulness meditation (MM) program by researchers from Massachusetts General Hospital, Bender Institute of Neuroimaging in Germany, and the University of Massachusetts Medical School. Researchers concluded that
..these findings may represent an underlying brain mechanism associated with mindfulness-based improvements in mental health.
The analgesic effect of MM involves multiple brain mechanisms including the activation of the anterior cingulate cortex and the ventromedial prefrontal cortex. In addition, brief periods of MM training increases the amount of grey matter in the hippocampus and parietal lobe. Other neural changes resulting from MM may increase the efficiency of attentional control.
Beyond its use in reducing depressive acuity, research additionally supports the effectiveness of mindfulness meditation upon reducing cravings for substances that people are addicted to. Addiction is known to involve the weakening of the prefrontal cortex that ordinarily allows for delaying of immediate gratification for longer term benefits by the limbic and paralimbic brain regions. Mindfulness meditation of smokers over a two-week period totaling 5 hours of meditation decreased smoking by about 60% and reduced their cravings, even for those smokers in the experiment who had no prior intentions to quit. Neuroimaging of those who practice mindfulness meditation has been shown to increase activity in the prefrontal cortex, a sign of greater self-control.
As part of treatment for substance abuse disorders (SUDs), conclusive data for efficacy is lacking, significant methodological limitations exist and it is unclear which people with SUDs might benefit most from mindfulness meditation (MM).
Attention and Mindfulness
Attention networks and mindfulness meditation
Psychological and Buddhists conceptualisations of mindfulness both highlight awareness and attention training as key components, in which levels of mindfulness can be cultivated with practise of mindfulness meditation. Focused attention meditation and open monitoring meditation are distinct types of mindfulness meditation, and the former relates to directing and maintaining attention on a chosen object (e.g. the breath). Open monitoring meditation does not involve focus on a specific object, and instead awareness is grounded in the perceptual features of one’s environment.
Focused attention meditation is typically practised first to increase the ability to enhance attentional stability, and awareness of mental states with the goal being to transition to open monitoring meditation practise that emphases the ability to monitor moment by moment changes in experience, without a focus of attention to maintain. Mindfulness meditation may lead to greater cognitive flexibility 
Neurological processes underlying focused attention meditation
It is considered that focused attention meditation entails the activation of attention networks in the following manner:
- Initially the alerting network of attention is activated involving sustaining attention on a chosen object. It is associated with the right parietal cortex, right frontal cortex and the thalamus 
- When mind wandering occurs this relates to activation of the default mode network associated with the following brain areas: the posterior cingulate cortex, posterior lateral parietal/temporal cortices, the cingulate cortex, and the parahippocampal gyrus. This attention network is associated with certain attentional states as introspective thought and daydreaming. Conversely, when de-activated it relates to task-engagement.
- Distraction from the focus of attention is detected by the salience network, and is associated with the task of monitoring the focus of attention. The associated brain regions include the cingulate cortex and the anterior insula 
- When a distracting thought grabs the focus of attention away from the chosen object, the executive function network is capable of inhibiting this from being further processed. This network reduces the distractibility of aspects of one’s environment, and is associated with the basal ganglia, lateral ventral cortex and the anterior cingulate cortex (ACC) 
- The orienting network of attention, which controls stimulus selection, involves shifting the focus of attention back to the original object. The superior colliculus and frontal eye fields as well as the temporal parietal junction and the superior parietal cortex are implicated.
Evidence for improvements in three areas of attention
Sustained attention Tasks of sustained attention relate to vigilance and the preparedness that aids completing a particular task goal. Psychological research into the relationship between mindfulness meditation and the sustained attention network have revealed the following:
- Mindfulness meditators have demonstrated superior performance when the stimulus to be detected in a task was unexpected, relative to when it was expected. This suggests that attention resources were more readily available in order to perform well in the task. This was despite not receiving a visual cue to aid performance. (Valentine & Sweet, 1999).
- In a Continuous performance task  an association was found between higher dispositional mindfulness and more stable maintenance of sustained attention.
- In an EEG study, the Attentional blink effect was reduced, and P3b ERP amplitude decreased in a group of participants that completed a mindfulness retreat. The incidence of reduced attentional blink effect relates to an increase in detectability of a second target. This may have been due to a greater ability to allocate attentional resources for detecting the second target, reflected in a reduced P3b amplitude.
- A greater degree of attentional resources may also be reflected in faster response times in task performance, as was found for participants with higher levels of mindfulness experience.
- Selective attention as linked with the orientation network, is involved in selecting the relevant stimuli to attend to.
- Performance in the ability to limit attention to potentially sensory inputs (i.e. selective attention) was found to be higher following the completion of an 8-week MBSR course, compared to a one-month retreat and control group (with no mindfulness training). The ANT task is a general applicable task designed to test the three attention networks, in which participants are required to determine the direction of a central arrow on a computer screen. Efficiency in orienting that represent the capacity to selectively attend to stimuli was calculated by examining changes in the reaction time that accompanied cues indicating where the target would occur relative to the aid of no cues.
- Meditation experience was found to correlate negatively with reaction times on a Eriksen flanker task measuring responses to global and local figures. Similar findings have been observed for correlations between mindfulness experience in an orienting score of response times taken from Attention Network Task performance.
Executive control attention Executive control attention include functions of inhibiting the conscious processing of distracting information. In the context of mindful meditation, distracting information would relate to attention grabbing mental events such as thoughts related to the future or past.
- More than one study have reported findings of a reduced Stroop effect following mindfulness meditation training. The Stroop effect indexes interference created by having words printed in colour that differ to the read semantic meaning e.g. green printed in red. However findings for this task are not consistently found. For instance the MBSR may differ to how mindful one becomes relative to a person who is already high in trait mindfulness.
- Using the Attention Network Task (a version of Eriksen flanker task  it was found that error scores that indicate executive control performance were reduced in experienced meditators  and following a brief 5 session mindfulness training program.
- A neuroimaging study supports behavioural research findings that higher levels of mindfulness are associated with greater proficiency to inhibit distracting information. As greater activation of the rostral anterior cingulate cortex (ACC) was shown for mindfulness meditators than matched controls. .
- Following a Stroop test, reduced amplitude of the P3 ERP component was found for a meditation group relative to control participants. This was taken to signify that mindfulness meditation improves executive control functions of attention. An increased amplitude in the N2 ERP component was also observed in the mindfulness meditation group, thought to reflect more efficient perceptual discrimination in earlier stages of perceptual processing.
Emotion regulation and Mindfulness
Approaching emotions in an adaptive way relates to mindful emotion regulation, which aims to decrease avoidance or suppression of emotions, as well as decreasing over-arousal in emotional reactivity in response to events. It is highlighted that emotion regulation is vital to mental stability. Over-involvement with emotions may lead to critical over-analysis of thoughts and emotions, characterising rumination, predictive of poor mental health. Reductions in rumination have been found following Mindfulness meditation practise. Under-involvement with addressing difficult emotions -termed avoidance behaviours- also can be problematic  as these can bring about maladaptive defences such as denial, suppression, cognitive distortions, development of psychoses, and even substance abuse or self-harm as methods of avoidance.
The mechanisms of Mindful emotion regulation
Through the initial foundations of attention control training, the focus of attention can more consciously be directed towards emotions that arise. Mindfulness combines this mechanism with a particular quality of attitudinal element, of acceptance and non-judgemental awareness. This can range from acknowledging ‘tightness in the chest’ or ‘increases in heart rate’ as well as thought content and emotions that arise. Subsequently, during mindfulness meditation, difficult emotions that may arise become paired with a compassionate and accepting attitude, which may gradually extinguish the fear of experiencing the emotions and any related thoughts. Mindfulness practise may lead to the development of metacognitive insight  or decentering. These concepts relate the experiencing thoughts as they are, which is changeable and transient, and that they are not characteristic of absolute reality. This may lead to increased cognitive flexibility  reflecting in more adaptively and consciously choosing mental content to identify with, rather than habitually responding. Alternatively a balanced and non-elaborative awareness of experience is cultivated, that is not as easily disrupted by the magnitude of emotions experienced or provocative external events.
Evidence of mindfulness and emotion regulation outcomes
Emotional reactivity can be measured and reflected in brain regions related to the production of emotions. It can also be reflected in tests of attentional performance, indexed in poorer performance in attention related tasks. The regulation of emotional reactivity as initiated by attentional control capacities can be taxing to performance, as attentional resources are limited 
- Patients with social anxiety disorder (SAD) exhibited reduced amygdala activation in response to negative self-beliefs following an MBSR intervention program that involves mindfulness meditation practise 
- The LPP ERP component indexes arousal and is larger in amplitude for emotionally salient stimuli relative to neutral. Individuals higher in trait mindfulness showed lower LPP responses to high arousal unpleasant images. These findings suggest that individuals with higher trait mindfulness were better able to regulate emotional reactivity to emotionally evocative stimuli.
- Participants that completed a 7-week mindfulness training program demonstrated a reduction in a measure of emotional interference (measured as slower responses times following the presentation of emotional relative to neutral pictures). This suggests a reduction in emotional interference.
- Following a MBSR intervention, decreases in social anxiety symptom severity were found, as well as increases in bilateral parietal cortex neural correlates. This is thought to reflect the increased employment of inhibitory attentional control capacities to regulate emotions 
Controversies in mindful emotion regulation
It is debated as to whether top-down executive control regions such as the Dorsolateral prefrontal cortex (DLPFC), are required  or not  to inhibit reactivity of the amygdala activation related to the production of evoked emotional responses. Arguably an initial increase in activation of executive control regions developed during mindfulness training may lessen with increasing mindfulness expertise 
A large part of mindfulness research is dependent on technology. As new technology continues to be developed, new imaging techniques will become useful in this field. It would be interesting to use real-time fMRI to help give immediate feedback and guide participants through the programs. It could also be used to more easily train and evaluate mental states during meditation itself. The new technology in the upcoming years offers many exciting potentials for the continued research.
Research on other types of meditation
Sahaja yoga and mental silence
Sahaja yoga meditation has been shown to correlate with particular brain and brain wave activity. Some studies have led to suggestions that Sahaja meditation involves 'switching off' irrelevant brain networks for the maintenance of focused internalized attention and inhibition of inappropriate information.
A study comparing practitioners of Sahaja Yoga meditation with a group of non meditators doing a simple relaxation exercise, measured a drop in skin temperature in the meditators compared to a rise in skin temperature in the non meditators as they relaxed. The researchers noted that all other meditation studies that have observed skin temperature have recorded increases and none have recorded a decrease in skin temperature. This suggests that Sahaja Yoga meditation, being a mental silence approach, may differ both experientially and physiologically from simple relaxation. Sahaja meditators scored above peer group for emotional wellbeing measures on SF-36 ratings.
Kundalini yoga meditation research has found that there "appears to produce structural as well as intensity changes in phenomenological experiences of consciousness", and that multiple regions of the brain are active.
Fifteen Carmelite nuns came from the monastery to the laboratory to enter a fMRI machine whilst meditating, allowing scientists there to scan their brains using fMRI while they were in a state known as Unio Mystica (and also Theoria). The documentary film Mystical Brain by Isabelle Raynauld examined this study.
Integrative body-mind training
A study involving the participation of a group of college students, who were asked to use a meditation technique called integrative body-mind training (IBMT involves body relaxation, mental imagery, and mindfulness training), concluded that "meditating may improve the integrity and efficiency of certain connections in the brain" through an increase in their number and robustness. Brain scans showed strong white matter changes in the anterior cingulate cortex.
The first Transcendental Meditation (TM) research studies were conducted at UCLA and Harvard University and published in Science and the American Journal of Physiology in 1970 and 1971. However, much research has been of poor quality, including a high risk for bias due to the connection of researchers to the TM organization and the selection of subjects with a favorable opinion of TM. Independent systematic reviews have not found health benefits for TM exceeding those of relaxation and health education. A 2013 statement from the American Heart Association described the evidence supporting TM as a treatment for hypertension as Level IIB, meaning that TM "may be considered in clinical practice" but that its effectiveness is "unknown/unclear/uncertain or not well-established".[this quote needs a citation]
Research on unspecified or multiple types of meditation
The medial prefrontal and posterior cingulate cortices have been found to be relatively deactivated during meditation (experienced meditators using concentration, lovingkindness and choiceless awareness meditation). In addition experienced meditators were found to have stronger coupling between the posterior cingulate, dorsal anterior cingulate, and dorsolateral prefrontal cortices both when meditating and when not meditating.
It was also observed that an eight-week MBSR course induced changes in gray matter concentrations.  Exploratory whole brain analyses identified significant increases in gray matter concentration in the PCC, TPJ, and the cerebellum. These results suggest that participation in MBSR is associated with changes in gray matter concentration in brain regions involved in learning and memory processes, emotion regulation, self-referential processing, and perspective taking.
Studies have shown that meditation has both short-term and long-term effects on various perceptual faculties. In 1984 a study showed that meditators have a significantly lower detection threshold for light stimuli of short duration. In 2000 a study of the perception of visual illusions by zen masters, novice meditators, and non-meditators showed statistically significant effects found for the Poggendorff Illusion but not for the Müller-Lyer Illusion. The zen masters experienced a statistically significant reduction in initial illusion (measured as error in millimeters) and a lower decrement in illusion for subsequent trials. Tloczynski has described the theory of mechanism behind the changes in perception that accompany mindfulness meditation thus: "A person who meditates consequently perceives objects more as directly experienced stimuli and less as concepts… With the removal or minimization of cognitive stimuli and generally increasing awareness, meditation can therefore influence both the quality (accuracy) and quantity (detection) of perception." Brown also points to this as a possible explanation of the phenomenon: "[the higher rate of detection of single light flashes] involves quieting some of the higher mental processes which normally obstruct the perception of subtle events."[this quote needs a citation] In other words, the practice may temporarily or permanently alter some of the top-down processing involved in filtering subtle events usually deemed noise by the perceptual filters.
Herbert Benson, founder of the Mind-Body Medical Institute, which is affiliated with Harvard University and several Boston hospitals, reports that meditation induces a host of biochemical and physical changes in the body collectively referred to as the "relaxation response". The relaxation response includes changes in metabolism, heart rate, respiration, blood pressure and brain chemistry. Benson and his team have also done clinical studies at Buddhist monasteries in the Himalayan Mountains. Benson wrote The Relaxation Response to document the benefits of meditation, which in 1975 were not yet widely known.
According to a March 2006 article in Psychological Bulletin, EEG activity begins to slow as a result of the practice of meditation. The human nervous system is composed of a parasympathetic system, which works to regulate heart rate, breathing and other involuntary motor functions, and a sympathetic system, which arouses the body, preparing it for vigorous activity. The National Institutes of Health (NIH) has written, "It is thought that some types of meditation might work by reducing activity in the sympathetic nervous system and increasing activity in the parasympathetic nervous system,"[this quote needs a citation] or equivalently, that meditation produces a reduction in arousal and increase in relaxation.
A study of GPs attending a meditation workshop found subsequent falls in their Kessler Psychological Distress Scale - 10 (K10) readings.
Mindfulness meditation, mindfulness of the breath, and related techniques, are intended to train attention for the sake of provoking insight. A wider, more flexible attention span makes it easier to be aware of a situation, easier to be objective in emotionally or morally difficult situations, and easier to achieve a state of responsive, creative awareness or "flow".
Slowing Ageing Process
Some researches were conducted to understand the malleable determinants of cellular aging, which is critical to understanding human longevity. The researchers concluded saying "We have reviewed data linking stress arousal and oxidative stress to telomere shortness. Meditative practices appear to improve the endocrine balance toward positive arousal (high DHEA, lower cortisol) and decrease oxidative stress. Thus, meditation practices may promote mitotic cell longevity both through decreasing stress hormones and oxidative stress and increasing hormones that may protect the telomere."
Potential adverse effects and limits of meditation
The following is an official statement from the US government-run National Center for Complementary and Alternative Medicine:
"Meditation is considered to be safe for healthy people. There have been rare reports that meditation could cause or worsen symptoms in people who have certain psychiatric problems, but this question has not been fully researched. People with physical limitations may not be able to participate in certain meditative practices involving physical movement. Individuals with existing mental or physical health conditions should speak with their health care providers prior to starting a meditative practice and make their meditation instructor aware of their condition."
Adverse effects have been reported, and may, in some cases, be the result of "improper use of meditation". The NIH advises prospective meditators to "ask about the training and experience of the meditation instructor… [they] are considering."
As with any practice, meditation may also be used to avoid facing ongoing problems or emerging crises in the meditator's life. In such situations, it may instead be helpful to apply mindful attitudes acquired in meditation while actively engaging with current problems. According to the NIH, meditation should not be used as a replacement for conventional health care or as a reason to postpone seeing a doctor.
Weaknesses in historic meditation research
In June, 2007 the United States National Center for Complementary and Alternative Medicine (NCCAM) published an independent, peer-reviewed, meta-analysis of the state of meditation research, conducted by researchers at the University of Alberta Evidence-based Practice Center. The report reviewed 813 studies involving five broad categories of meditation: mantra meditation, mindfulness meditation, yoga, T'ai chi, and Qigong, and included all studies on adults through September 2005, with a particular focus on research pertaining to hypertension, cardiovascular disease, and substance abuse.
The report concluded, "Scientific research on meditation practices does not appear to have a common theoretical perspective and is characterized by poor methodological quality. Firm conclusions on the effects of meditation practices in healthcare cannot be drawn based on the available evidence. Future research on meditation practices must be more rigorous in the design and execution of studies and in the analysis and reporting of results." (p. 6) It noted that there is no theoretical explanation of health effects from meditation common to all meditation techniques.
A version of this report subsequently published in the Journal of Alternative and Complementary Medicine stated that "Most clinical trials on meditation practices are generally characterized by poor methodological quality with significant threats to validity in every major quality domain assessed". This was the conclusion despite a statistically significant increase in quality of all reviewed meditation research, in general, over time between 1956 and 2005. Of the 400 clinical studies, 10% were found to be good quality. A call was made for rigorous study of meditation. These authors also noted that this finding is not unique to the area of meditation research and that the quality of reporting is a frequent problem in other areas of complementary and alternative medicine (CAM) research and related therapy research domains.
Of more than 3,000 scientific studies that were found in a comprehensive search of 17 relevant databases, only about 4% had randomised controlled trials (RCTs), which are designed to exclude the placebo effect.
A 2013 statement from the American Heart Association evaluated the evidence for the effectiveness of TM as a treatment for hypertension as "unknown/unclear/uncertain or not well-established", and stated: "Because of many negative studies or mixed results and a paucity of available trials... other meditation techniques are not recommended in clinical practice to lower BP at this time."
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- Buddhism and psychology
- Buddhist meditation
- Mindfulness (psychology)
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