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Surveys & evaluates various meditative practices & evidence of neurophysiological benefits From Wikipedia, the free encyclopedia
The psychological and physiological effects of meditation have been studied. In recent years, studies of meditation have increasingly involved the use of modern instruments, such as functional magnetic resonance imaging and electroencephalography, which are able to observe brain physiology and neural activity in living subjects, either during the act of meditation itself or before and after meditation. Correlations can thus be established between meditative practices and brain structure or function.[1]
Since the 1950s hundreds of studies on meditation have been conducted, but many of the early studies were flawed and thus yielded unreliable results.[2][3] Another major review article also cautioned about possible misinformation and misinterpretation of data related to the subject.[4][5] Contemporary studies have attempted to address many of these flaws with the hope of guiding current research into a more fruitful path.[6]
However, the question of meditation's place in mental health care is far from settled and there is no general consensus among experts. Though meditation is generally deemed useful, recent meta-analyses show small-to-moderate effect sizes. This means that the effect of meditation is roughly comparable to that of the standard measures of self-care like sleep, exercise, nutrition and social intercourse. Importantly, it has a worse safety profile than these standard measures (see section on adverse-effects).[7][8][9][10][11] A recent meta-analysis also indicates that the increased mindfulness experienced by mental health patients may not be the result of explicit mindfulness interventions but more of an artefact of their mental health condition (e.g., depression, anxiety) as it is equally experienced by the participants that were placed in the control condition (e.g., active controls, waiting list). This raises further questions as to what exactly meditation does, if anything, that is significantly different from the heightened self-monitoring and self-care that follows in the wake of spontaneous recovery or from the positive effects of encouragement and care that is usually provided in ordinary health-care settings (see section on the difficulties studying meditation).[12] There also seems to be a critical moderation of the effects of meditation according to individual differences. In one meta-analysis from 2022, involving a total of 7782 participants, the researchers found that a higher baseline level of psychopathology (e.g., depression) was associated with deterioration in mental health after a meditation intervention, and thus was contraindicated.[13]
A previous study commissioned by the US Agency for Healthcare Research and Quality found that meditation interventions reduce multiple negative dimensions of psychological stress.[10] Other systematic reviews and meta-analyses show that mindfulness meditation has several mental health benefits such as bringing about reductions in depression symptoms,[14][15][16] improvements in mood,[17] stress-resilience[17] and attentional control.[17] Mindfulness interventions also appear to be a promising intervention for managing depression in youth.[18][19] Mindfulness meditation is useful for managing stress,[15][20][21][17] anxiety[14][15][21] and also appears to be effective in treating substance use disorders.[22][23][24] A recent meta-analysis by Hilton et al. (2016) including 30 randomized controlled trials found high quality evidence for improvement in depressive symptoms.[25] Other review studies have shown that mindfulness meditation can enhance the psychological functioning of breast cancer survivors,[15] is effective for people with eating disorders[26][27] and may also be effective in treating psychosis.[28][29][30]
Studies have also shown that rumination and worry contribute to mental illnesses such as depression and anxiety,[31] and mindfulness-based interventions are effective in the reduction of worry.[31][32] Some studies suggest that mindfulness meditation contributes to a more coherent and healthy sense of self and identity, when considering aspects such as sense of responsibility, authenticity, compassion, self-acceptance and character.[33][34]
The analgesic effect of mindfulness meditation may involve multiple brain mechanisms, of which, chronic pain is shown to have a small decrease when performing meditation.[35] Current research demonstrates a lack of high-quality data to support a strong case for clinical prescription of meditation, however future research may further change our understanding of chronic pain treatment and mindfulness,[36] but there are too few studies to allow conclusions about its effects on chronic pain.[37]
The act of mindful meditation creates alterations in the brain that lead to a heightened ability to improve emotions.[38] In an 8-week mindfulness meditation study, Gotink et al. discovered that amygdala, insula, cingulate cortex, and hippocampus activity decreased.[38] Importantly, these short-term changes are often equated to a brain with longer time spent doing mindfulness meditation and interventions, such as months or years. Another meta-analysis found preliminary evidence for effects in the prefrontal cortex and other brain regions associated with body awareness.[39] However, these results should be interpreted with caution as funnel plots indicate that publication bias is an issue in meditation research.[40] A 2016 review using 78 functional neuroimaging studies suggests that different meditation styles are associated with different brain activity.[41] While other studies have found structural changes in the brain may occur, but most studies have utilized weak methodology.[40]
Psychological and Buddhist conceptualizations of mindfulness both highlight awareness and attention training as key components, in which levels of mindfulness can be cultivated with practice of mindfulness meditation.[42][17] Focused attention meditation (FAM) and open monitoring meditation (OMM) are distinct types of mindfulness meditation; FAM refers to the practice of intently maintaining focus on one object, whereas OMM is the progression of general awareness of one's surroundings while regulating thoughts.[43][44] Some forms of Buddhist mindfulness meditation may lead to greater cognitive flexibility.[45]
In an active randomized controlled study completed in 2019, participants who practiced mindfulness meditation demonstrated a greater improvement in awareness and attention than participants in the active control condition.[17] Alpha wave neural oscillation power (which is normally associated with an alert resting state) has been shown to be increased by mindfulness in both healthy subjects and patients.[46]
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:
Research shows meditation practices lead to greater emotional regulation abilities. Mindfulness can help people become more aware of thoughts in the present moment, and this increased self-awareness leads to better processing and control over one's responses to surroundings or circumstances.[61][62]
Positive effects of this heightened awareness include a greater sense of empathy for others, an increase in positive patterns of thinking, and a reduction in anxiety.[62][61] Reductions in rumination also have been found following mindfulness meditation practice, contributing to the development of positive thinking and emotional well-being.[63]
Emotional reactivity can be measured and reflected in brain regions related to the production of emotions.[64] 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.[65]
It is debated as to whether top-down executive control regions such as the dorsolateral prefrontal cortex (DLPFC),[75] are required[73] or not[66] 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.[76]
Furthermore, current research data is inconclusive and incomplete in linking positive effects of mindful meditation with a variety of reported positive effects. Additional high-fidelity studies are needed before a more complete understanding of the full effects of mindfulness can be reached.[36][38][35]
Research has shown stress reduction benefits from mindfulness.[77][78][79] A 2019 study tested the effects of meditation on the psychological well-being, work stress, and blood pressure of employees working in the United Kingdom. One group of participants were instructed to meditate once a day using a mindfulness app on their smartphones, while the control group did not engage in meditation. Measurements of well-being, stress, and perceived workplace support were taken for both groups before the intervention and then again after four months. Based on self-report questionnaires, the participants who engaged in meditation showed a significant increase in psychological well-being and perceived workplace support. The meditators also reported a significant decrease in anxiety and stress levels.[79]
Another study conducted to understand association between mindfulness, perceived stress and work engagement indicated that mindfulness was associated with lower perceived stress and higher work engagement.[80]
Other research shows decreased stress levels in people who engage in meditation after shorter periods of time as well. Evidence of significant stress reduction was found after only three weeks of meditation intervention.[17] Brief, daily meditation sessions can alter one's behavioral response to stressors, improving coping mechanisms and decreasing the adverse impact caused by stress.[81][82] A study from 2016 examined anxiety and emotional states of naive meditators before and after a seven-day meditation retreat in Thailand. Results displayed a significant reduction in perceived stress after this traditional Buddhist meditation retreat.[82]
Chronic insomnia is often associated with anxious hyperarousal and frustration over inability to sleep.[83] Mindfulness has been shown to reduce insomnia and improve sleep quality, although self-reported measures show larger effects than objective measures.[83][84]
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. Real-time fMRI might give immediate feedback and guide participants through the programs. It could also be used to more easily train and evaluate mental statesFunctional magnetic resonance imaging during meditation itself.[85]
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Vipassana or "insight" meditation is a form of mindfulness meditation believed[by whom?] to have been taught by the Buddha Gautama. The practice aims to increase a sense of awareness of the present moment. The practitioner becomes a quiet observer of their thoughts, emotions, and sensations; allowing them to come and go without passing judgement.[86][87] A plethora of evidence now exists to suggest that vipassana meditation does indeed lead to increased mindfulness, but the benefits of the practice do not stop there. It has also been found to reduce stress and increase both self-kindness and overall well-being.[88]
Electroencephalography studies on Vipassana meditators seemed to indicate significant increase in parieto-occipital gamma rhythms in experienced meditators (35–45 Hz).[89] In another study conducted by NIMHANS on Vipassana meditators, researchers found readings associated with improved cognitive processing after a session of meditation, with distinct and graded difference in the readings between novice meditators and experienced meditators.[90]
Khoury and colleagues (2017) conducted a meta-analysis including a total of 21 studies and 2,912 participants. The study aimed to evaluate the effects of traditional vipassana meditation retreats in various populations including advanced meditators, novice meditators, and incarcerated individuals. More specifically, it explored the psychological outcomes including anxiety symptoms, depressive symptoms, and stress following the retreats, evaluated the impacts of the retreats on levels of mindfulness, and explored variables moderating the effectiveness of traditional retreats. Results suggested that traditional vipassana meditation retreats were moderately effective at improving psychological outcomes, with novice meditators and members of the general population experiencing particularly large reductions in anxiety, depression, and stress when compared to both experienced meditators and incarcerated individuals. Moreover, the results suggested an increased capacity for emotional regulation, acceptance, compassion, and mindfulness as well as higher quality of life scores following the retreats across all populations. These results held steady even at follow-up.[91]
An essential component to the Vipassana mediation approach is the focus on awareness, referring to bodily sensations and psychological status. In a study conducted by Zeng et al. (2013), awareness was described as the acknowledgement of consciousness which is monitoring all aspects of the environment.[92] This definition differentiates the concept of awareness from mindfulness. The emphasis on awareness, and the way it assists in monitoring emotion, is unique to this meditative practice.
Kundalini yoga has proved to increase the prevention of cognitive decline and evaluate the response of biomarkers to treatment, thereby shedding light on the underlying mechanisms of the link between Kundalini Yoga and cognitive impairment. For the study, 81 participants aged 55 and older who had subjective memory complaints and met criteria for mild cognitive impairment, indicated by a total score of 0.5 on the Clinical Dementia Rating Scale. The results showed that at 12 weeks, both the yoga group showed significant improvements in recall memory and visual memory and showed a significant sustained improvement in memory up to the 24-week follow-up, the yoga group showed significant improvement in verbal fluency and sustained significant improvements in executive functioning at week 24. In addition, the yoga cohort showed significant improvement in depressive symptoms, apathy, and resilience from emotional stress. This research was provided by Helen Lavretsky, M.D. and colleagues.[93] In another study, Kundalini Yoga did not show significant effectiveness in treating obsessive-compulsive disorders compared with Relaxation/Meditation.[94]
Sahaja yoga meditation is regarded as a mental silence meditation, and has been shown to correlate with particular brain[95][96] and brain wave[97][98][99] characteristics. One study has led to suggestions that Sahaja meditation involves 'switching off' irrelevant brain networks for the maintenance of focused internalized attention and inhibition of inappropriate information.[100] Sahaja meditators appear to benefit from lower depression[101] and scored above control group for emotional well-being and mental health measures on SF-36 ratings.[102][103][104]
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.[99]
In a 2006 review, Transcendental Meditation proved comparable with other kinds of relaxation therapies in reducing anxiety.[94] In another 2006 review, study participants demonstrated a one Hertz reduction in electroencephalography alpha wave frequency relative to controls.[105]
A 2012 meta-analysis published in Psychological Bulletin, which reviewed 163 individual studies, found that Transcendental Meditation performed no better overall than other meditation techniques in improving psychological variables.[106]
A 2013 statement from the American Heart Association said that Transcendental Meditation could be considered as a treatment for hypertension, although other interventions such as exercise and device-guided breathing were more effective and better supported by clinical evidence.[107]
A 2014 review found moderate evidence for improvement in anxiety, depression and pain with low evidence for improvement in stress and mental health-related quality of life.[108][109]
Transcendental Meditation may reduce blood pressure, according to a 2015 review that compared it to control groups. A trend over time indicated that practicing Transcendental Meditation may lower blood pressure. Such effects are comparable to other lifestyle interventions. Conflicting findings across reviews and a potential risk of bias indicated the necessity of further evidence.[110][111]
Several meta-analyses have examined the effects of mindful meditation on one’s loving, kindness, and compassionate disposition and behaviors. Significant increases in self-reported self-compassion. Compassion, and well-being were reported alongside decreases in depression and anxiety.[112] Another study indicated an increase in positive emotions.[113][114] There may be further benefits that are yet to be discovered, with only preliminary data on mindfulness and mediation. Further studies and explorations into the effects of mindful meditation on the self are needed to draw further conclusions.[114][113][112]
The medial prefrontal and posterior cingulate cortices have been found to be relatively deactivated during meditation by experienced meditators using concentration, loving-kindness, and choiceless awareness meditation.[115] 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.[116] Over time meditation can actually increase the integrity of both gray and white matter. The added amount of gray matter found in the brain stem after meditation improves communication between the cortex and all other areas within the brain.[117][118] Meditation often stimulates a large network of cortical regions including the frontal and parietal regions, lateral occipital lobe, the insular cortex, thalamic nuclei, basal ganglia, and the cerebellum region in the brain. These parts of the brain are connected with attention and the default network of the brain which is associated to day dreaming.[119]
In addition, both meditation and yoga have been found to have impacts on the brain, specifically the caudate.[121] Strengthening of the caudate has been shown in meditators as well as yogis. The increased connectedness of the caudate has potential to be responsible for the improved well-being that is associated with yoga and meditation.[120]
Meditation is under preliminary research to assess possible changes in grey matter concentrations.[40]
Published research suggests that meditation can facilitate neuroplasticity and connectivity in brain regions specifically related to emotion regulation and attention.[122][123]
Non-directive forms of meditation where the meditator lets their mind wander freely can actually produce higher levels of activity in the default mode network when compared to a resting state or having the brain in a neutral place.[124][125] These Non directive forms of meditation allows the meditators to have better control over thoughts during everyday activities or when focusing on specific task due to a reduced frustration at the brains mind wandering process.[125] When given a specific task, meditation can allow quicker response to changing environmental stimuli. Meditation can allow the brain to decrease attention to unwanted responses of irrelevant environmental stimuli and a reduces the Stroop effect. Those who meditate have regularly demonstrated more control on what they focus their attention on while maintaining a mindful awareness on what is around them.[126] Experienced meditators have been shown to have an increased ability when it comes to conflict monitoring[17] and find it easier to switch between competing stimuli.[127] Those who practice meditation experience an increase of attentional resources in the brain and steady meditation practice can lead to the reduction of the attentional blink due to a decreased mental exertion when identifying important stimuli.[127]
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.[128] 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.[129] 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."[129] Brown 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."[130] 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.[130]
Meditation enhances memory capacity specifically in the working memory and increases executive functioning by helping participants better understand what is happening moment for moment.[131][132] Those who meditate regularly have demonstrated the ability to better process and distinguish important information from the working memory and store it into long-term memory with more accuracy than those who do not practice meditation techniques.[118] Meditation may be able to expand the amount of information that can be held within working memory and by so doing is able to improve IQ scores and increase individual intelligence.[124] The encoding process for both audio and visual information has been shown to be more accurate and detailed when meditation is used.[127] Though there are limited studies on meditation's effects on long-term memory, because of meditations ability to increase attentional awareness, episodic long-term memory is believed to be more vivid and accurate for those who meditate regularly. Meditation has also shown to decrease memory complaints from those with Alzheimer's disease which also suggests the benefits meditation could have on episodic long-term memory which is linked to Alzheimer's.[133]
Electroencephalography activity slows as a result of meditation.[134] Some types of meditation may lead to a calming effect by reducing sympathetic nervous system activity while increasing parasympathetic nervous system activity. Or, equivalently, that meditation produces a reduction in arousal and increase in relaxation.[135]
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".[136] 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.[137] Benson wrote The Relaxation Response to document the benefits of meditation, which in 1975 were not yet widely known.[138]
There is no good evidence to indicate that meditation affects the brain in aging.[139]
Studies have shown meditators to have higher happiness than control groups, although this may be due to non-specific factors such as meditators having better general self-care.[140][141][102][101]
Positive relationships have been found between the volume of gray matter in the right precuneus area of the brain and both meditation and the subject's subjective happiness score.[142][143][144][145][40][146] A recent study found that participants who engaged in a body-scan meditation for about 20 minutes self-reported higher levels of happiness and decrease in anxiety compared to participants who just rested during the 20-minute time span. These results suggest that an increase in awareness of one's body through meditation causes a state of selflessness and a feeling of connectedness. This result then leads to reports of positive emotions.[147]
A technique known as mindfulness-based stress reduction (MBSR) displays significant benefits for mental health and coping behaviors. Participants who had no prior experience with MBSR reported a significant increase in happiness after eight weeks of MBSR practice. Focus on the present moment and increased awareness of one's thoughts can help monitor and reduce judgment or negative thoughts, causing a report of higher emotional well-being.[148] The MBSR program and evidence for its effectiveness is described in Jon Kabat-Zinn's book Full Catastrophe Living.[149]
Meditation has been shown to reduce pain perception.[150] An intervention known as mindfulness-based pain management (MBPM) has been subject to a range of studies demonstrating its effectiveness.[151][152]
Meditation and mindfulness have also been correlated with unpleasant experiences, but the potential for adverse effects from meditation has received limited attention in scientific articles[153][154][155][web 1] and the popular press.[web 2][web 3][web 4][web 5]
According to Farias et al. (2020) the most common adverse effects of meditation are anxiety and depression.[153] Other adverse affects may include depersonalization[153] or altered sense of self or the world,[156] distorted emotions or thoughts, and, in a few cases, visual and auditory psychosis, and with pre-existing historical factors suicide.[153][157][158][159]
Schlosser et al. (2019) reported that, of 1,232 regular meditators with at least two months of meditation experience, about a quarter reported having had particularly unpleasant meditation-related experiences (such as anxiety, fear, distorted emotions or thoughts, altered sense of self or the world), which they thought may have been caused by their meditation practice. Meditators with high levels of repetitive negative thinking and those who only engage in deconstructive meditation were more likely to report unpleasant side effects. Adverse effects were less frequently reported in women and religious meditators.[160]
Meditation also has an addictive potential as it both offers biochemical rewards and socially acceptable avenues for escapism (like internet use, social media, substance abuse).[161][162] Using spiritual ideas and practices "to sidestep or avoid facing unresolved emotional issues, psychological wounds, and unfinished developmental tasks"[163] is known as Spiritual bypass, a term introduced in the mid 1980s by John Welwood, a Buddhist teacher and psychotherapist.[163]
"Zen sickness", exhaustion caused by prolonged intense practice and self-neglect is described by Hakuin[164] and Bankei.
In recent years both the soundness of the scientific foundations and the desirability of the societal effects of mindfulness have been questioned.[165][166][167][168]
Britton et al. (2019), in a study on the effects of mindfulness-based programs (MBPs), found negative side-effects in 37% of the sample while lasting bad effects in 6–14% of the sample.[169] Most of the side effects were related to signs of dysregulated arousal (i.e., hyperarousal and dissociation). The majority of these adverse events occurred as a result of regular practice at home or during class something that challenges the notion that it is only intense practice that can give rise to negative experiences; as it turns out intense all-day retreats or working with difficulty practice accounts for only 6% of adverse effects. The symptoms most readily recognized as negative were those of hyperarousal (e.g., anxiety and insomnia). On the other hand, while dissociation symptoms (e.g., emotional blunting, derealization, and self-disturbance) were both less frequent and less likely to be appraised as negative, they were still associated with more than 5–10 times greater risk for lasting bad effects… This means that re-appraisal of dissociative symptoms via non-judgmental acceptance is not sufficient to prevent impairment in functioning and should not constitute the only response. Instead, training in how to recognize dissociative symptoms as potential indicators of the need for intervention, which have recently been added to some mindfulness teacher training programs may be important.[170]
There is also mounting evidence that mindfulness can disturb various prosocial behaviors. By blunting emotions, in particular the social emotions of guilt and shame, it may produce deficits in the feelings of empathy and remorse thus creating calm but callous practitioners. Hafenbrack et al. (2022), in a study on mindfulness with 1400 participants, found that focused-breathing meditation can dampen the relationship between transgressions and the desire to engage in reparative prosocial behaviors.[171] Poullin et al. (2021) found that mindfulness can increase the trait of selfishness. The study, consisting of two interrelated parts and totaling 691 participants, found that a mindfulness induction, compared to a control condition, led to decreased prosocial behavior. This effect was moderated by self-construals such that people with relatively independent self-construals became less prosocial while people with relatively interdependent self-construals became more so. In the western world where independent self-construals generally predominate meditation may thus have potentially detrimental effects.[172]
These new findings about mindfulness' socially problematic effects imply that it can be contraindicated to use mindfulness as a tool to handle acute personal conflicts or relational difficulties; in the words of Andrew Hafenbrack, one of the authors of the study, “If we 'artificially' reduce our guilt by meditating it away, we may end up with worse relationships, or even fewer relationships”.[173][171] In line with this, a meta-analysis by Kreplin et al. (2018) concluded that meditation only has a limited effect in increasing prosocial behaviours (e.g., empathy, compassion).[11]
Mindfulness is not helpful if it used to avoid facing ongoing problems or emerging crises in the meditator's life, in which case it will function as just another form of experiential avoidance and potentially exacerbate the crisis. In such situations, it may instead be helpful to apply mindful attitudes while actively engaging with current problems.[174][page needed] According to the NIH, meditation and mindfulness should not be used as a replacement for conventional health care or as a reason to postpone seeing a doctor.[175]
Organizations such as Cheetah House and Meditating in Safety document research on problems arising in meditation, and offer help for meditators in distress or those recovering from meditation-related health problems. In some cases, adverse effects may be attributed to "improper use of meditation"[176] or the aggravation of a preexisting condition; however, developing research in this area suggests the need for deeper engagement with the causes of severe distress, which previous "meditation teachers have perhaps too quickly and rather insensitively dismissed as pre-existing or unrelated psychopathology".[177] Where meditation is prescribed or offered as a treatment,
principles of informed consent require that treatment choice be based in part on the balance of benefits to harms, and therefore can only be made if harms are adequately measured and known.[178]
In June 2007, the United States National Center for Complementary and Integrative Health 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, tai 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. 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.[2]
A version of this report subsequently published in the Journal of Alternative and Complementary Medicine in 2008 stated: "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 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.[6] 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.[2]
In a 2013 meta-analysis, Awasthi argued that meditation is defined poorly and despite the research studies showing clinical efficacy, exact mechanisms of action remain unclear.[179] A 2017 commentary was similarly mixed,[4][5] with concerns including the particular characteristics of individuals who tend to participate in mindfulness and meditation research.[180]
A 2013 statement from the American Heart Association evaluated the evidence for the effectiveness of Transcendental Meditation 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."[181] According to the American Heart Association, while there are promising results about the impact of meditation in reducing blood pressure and managing insomnia, depression and anxiety, it is not a replacement for healthy lifestyle changes and is not a substitute for effective medication.[182]
The term meditation encompasses a wide range of practices and interventions rooted in different traditions, but research literature has sometimes failed to adequately specify the nature of the particular meditation practice(s) being studied.[183] Different forms of meditation practice may yield different results depending on the factors being studied.[183]
The presence of a number of intertwined factors including the effects of meditation, the theoretical orientation of how meditation practices are taught, the cultural background of meditators, and generic group effects complicates the task of isolating the effects of meditation:[77]
Numerous studies have demonstrated the beneficial effects of a variety of meditation practices. It has been unclear to what extent these practices share neural correlates. Interestingly, a recent study compared electroencephalogram activity during a focused-attention and open monitoring meditation practice from practitioners of two Buddhist traditions. The researchers found that the differences between the two meditation traditions were more pronounced than the differences between the two types of meditation. These data are consistent with our findings that theoretical orientation of how a practice is taught strongly influences neural activity during these practices. However, the study used long-term practitioners from different cultures, which may have confounded the results.[184]
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