The Myth Of The Relaxation Response

by David Orme-Johnson, Ph.D.
Reprinted from Truth About TM

Abstract
Although relaxation and meditation techniques have been hypothesized to produce the so-called relaxation response, a review of the literature finds that the acute physiological changes that occur during most techniques are not significantly different from uninstructed rest, sitting eyes closed. Compared to rest, some techniques produce specific acute changes resulting from their specific methodologies, such as reduced muscle tension in muscle relaxation techniques, reduced respiration according to the well known orienting response in techniques that require focused attention, and reflexive entrainment of the heart rate with the breath for techniques that control respiration.

The relaxation response was originally modeled on the changes produced by the Transcendental Meditation® (TM®) technique, but some changes that occur during TM, such as increased cardiac output, skin conductance, and plasma adrenaline, are in the opposite direction of the relaxation response, and many other changes, such as increased cerebral blood flow and EEG coherence, are unpredicted by the relaxation response. With regard to clinical outcomes, randomized clinical trials that controlled for expectation, placebo, and other design features, as well as meta-analyses and reviews of over 790 studies, provide strong evidence that different techniques are not equivalent and they have specific effects. For example, it appears that muscular disorders are best treated with muscularly oriented methods, while autonomic dysfunction such as hypertension and migraine headaches are more effectively treated with techniques that target the autonomic nervous system. The Transcendental Meditation technique appears to be the most effective treatment overall for a broad range of stress-related disorders, including hypertension, anxiety, substance abuse, and mental health.

Introduction
Herbert Benson and colleagues proposed that different meditation and relaxation techniques with a wide range of methodologies and goals produce in common a "relaxation response", that is, decreased sympathetic nervous system activity, opposite to the "fight or flight' response, and that the medical, psychological, and behavioral effects of these different techniques are therefore equivalent. 1-5 This review examines all relevant documents found in Medline and the psychology literature using the search words "relaxation response", and all studies found comparing different relaxation and meditation techniques, including 11 meta-analyses (including three that were synthesized into a later one) and 33 reviews (including reviews covered by later reviews), all in all synthesizing approximately 790 studies. Part I covers acute physiological changes that occur during the various techniques, and Part II covers their medical and other short and long-term benefits.

Part I: Acute Effects
The relaxation response was modeled after the Transcendental Meditation technique (TM): "The studies of Transcendental Meditation suggested the existence of a physiological response which could be elicited by other techniques" (p. 115). 6 Wallace and colleagues found that TM decreased O2 consumption, respiratory rate, heart rate, muscle tension, and blood pressure and increased skin resistance and EEG alpha waves to a greater extent than uninstructed rest while just sitting with eyes closed. 7-9 These are basically a list of the changes said to constitute the relaxation response.1-3

Techniques specifically mentioned as producing the relaxation response include Progressive Relaxation, Hypnosis, Cotention (concentration on one thing exclusively as opposed to Ditention or ordinary wakefulness in which attention shifts from object to object), Shavasan (a yoga posture lying still, face up), Autogenic Training, Sentic Cycles (a self-induced emotional experience), Zen, Zazen, Yoga, Mindfulness, the Transcendental Meditation technique (TM), and various types of meditative prayer from Eastern and Western traditions.1, 3-5 In addition, Benson and colleagues created their own technique, which has been widely referred to in the literature as the "Benson technique". 10-12

The Benson technique
The first study of the Benson technique (BT) found a 10% reduction in O2 consumption during a 12-minute period relative to an equivalent period of unstructured eyes closed resting. 6 This is 60% less than the reduction of 16% for TM in the same amount of time 7, 8 using comparable subjects (undergraduates of both sexes, mean age of 24 years) and methodologies (mouth piece or mask with a Beckman gas analyzer). In the TM study, the baseline level of O2 consumption was 246.8 ml/min and decreased to 206.5 ml/min after 12 minutes (interpolated from the 10 and 20 minute measurement). 7 For BT, the change went from 251.4 ml/min during rest to 225.4 ml/min. The level of O2 consumption was thus 8.4% lower during TM than during BT (t(23)=2.05, p<.06, trend), and the level of CO2 elimination was 173.9 ml/min during TM compared to 214.1 ml/min for the BT, a significant 18.7% difference (t(23)=2.56, p=.02). An independent study by Cork and Cox of the Stress Research unit of Nottingham University, England, instructed subjects who "listened to taped relaxation instructions taken from Beary and Benson and then practiced the technique" (p. 102). 11 They found: "The heart speeds up during inspiration and then slows down during expiration, thereby producing sinus arrhythmia"(p. 105)11 Other than producing sinus arrhythmia, which is a well known effect of controlling breathing,13 Cork and Cox found that BT did not produce changes in blood pressure and heart rate different from the baseline condition and control condition. In a second study comparing BT to resting, they report: "However, these [reductions on blood pressure, pulse, and mood] occurred both when subjects were practicing Benson's technique and when they were simply resting quietly. There were, therefore, no differential effects of the two procedures on psychophysiological state" (p. 107).11 They further note: "Pollack and Zeiner (1979) 14 found no significant differences in the psychophysiological effect of Benson's technique, uninstructed relaxation, and sitting quietly . The only procedure causing any significant change was sitting quietly which led to the greatest reductions in heart rate" (p. 110). 11 Recently, Benson and colleagues report reduced frontal beta EEG activity during BT, but no significant changes for any other frequency band or scalp location. 15 This is different from the original specification of the relaxation response, which included increased alpha waves, 1 and it is different from the physiology of the TM technique in which alpha and theta increase.7-9, 16, 17 Moreover, beta activity has been observed to increase in some phases of the TM technique.16 Progressive relaxation
Edelman (1970) reported two studies indicating that the psychophysiological effects of progressive relaxation were no different from three control conditions: suggestion of relaxation, instruction for skeletal movement (taken from the relaxation instructions), and continuous semi-classical music.18

Hypnosis
Hypnotic suggestion ‘to relax’ or ‘to sleep’ does not reduce metabolic rate or produce relaxation to a greater extent than baseline level during sitting eyes closed prior to the suggestion. 19-21 Benson and colleagues have argued that the baseline was already a state of relaxation due to hypnotic induction, 1 but research shows that there is nothing special about the physiology of the ‘hypnotic trance’ or ‘hypnotic sleep.’ 19-23

Autogenic Training
Galois of the Centre Hospitalier Saint-Philibert in Lomme, France, compared autogenic training (AT),24 TM, and uninstructed rest (C) in 30 normal subjects, mean age 27. 25 Spontaneous skin resistance responses decreased during both TM and AT compared to C. However, respiration rate decreased more during TM than AT or C, and TM had more respiratory suspensions than the other two groups, without hypercapnia or hyperpnea, indicating a natural state of deep rest. Also, spontaneous skin resistance responses, respiration rate, and reaction time, which were similar between groups before the practice, were all significantly lower after the practice for TM than the other two groups.

Cotention
Cotention has been shown to reduce respiration rate, but no studies are cited showing that it affects any of the other parameters of the 'relaxation response.' 1 Moreover, the orienting response can account for the slowing of breathing during focusing. During the orienting response, initially the breath slows down, and then continues at a slower rate than before the orienting process.26, 27

Shavasan
Shavasan is a yoga posture of lying still, face up. Dhanaraj and Singh of the University of Alberta, Canada, compared Shavasan with TM and found that TM produced significantly greater reductions in O2 consumption, and tidal volume. 28

Yoga, Zen
Many of the early studies on meditation were on traditional Yoga and Zen meditation techniques, which do appear to produce a generalized reduction in sympathetic nervous system activity, 29-34 as Wallace has pointed out. 7 However, Wallace also noted that there were important differences in techniques, e.g., the non-habituation of the EEG alpha blocking response in Zen monks compared to loss of the alpha blocking in some of the yogis. 7, 29, 30 These studies were on very few subject, sometimes just one, and most studies did not have control groups. Moreover, the subjects were Yoga experts and Zen masters of ten to twenty years practice, following a religious way of life, and their generalization to the Western lifestyle is questionable.

Mindfulness Meditation
Two studies, one on pain and the other on psychosomatic complaints, utilized mindfulness meditation to elicit the relaxation response. 35, 36 In the context of chronic pain, mindfulness means “detached observation of the pain experience,” and the technique involves putting attention onto the pain area. 37 This literature search found no physiological evidence that mindfulness meditation elicits the relaxation response.

Transcendental Meditation technique
A meta-analysis of 32 studies comparing TM and ordinary eyes closed resting showed that TM is different from rest in some, but not all, ways that the relaxation response would predict. 38 Respiration rate and plasma lactate decrease and basal skin resistance increases, but heart rate, the most commonly measured index of the relaxation response, did not change more during TM than rest. Another index of sympathetic arousal, spontaneous skin resistance responses, also did not discriminate TM from rest. In addition, blood pressure does not change acutely during the TM technique in normal subjects, 7-9 whereas blood pressure reduction is said to be one the parameters of the relaxation response. 1

This meta-analysis also found during the pre TM or rest baseline that practitioners of TM had lower levels of heart rate, respiration rate, plasma lactate, and spontaneous skin resistance responses than rest controls, indicating that the reductions during the practice were not due to regression to the mean. 38

Since the effects of the relaxation response were originally modeled after the TM technique, 4, 6 it is important to note that some of the physiological changes during TM, such as increased cardiac output, 39 increased plasma adrenaline in long-term TM practitioners (despite decreased heart rate), 40 and increased cerebral blood flow39, 41 are in the opposite direction of the relaxation response. Other changes during TM are simply not predicted by the relaxation response, such as decreased hepatic and renal blood flow, 39 decreased tissue metabolism, 42 modulation of red cell metabolism, 43 increased prolactin, 44 increased serotonin metabolite, 45-47 short- and long-term changes in pituitary hormone levels, indicative of increased stability and sensitivity in endocrine control systems (TSH, GH, and prolactin), 48 increased plasma phenylalanine, 49 increased salivary electrolytes and protein and decreased salivary pH, 50 high voltage theta bursts, 8, 16, 51 EEG beta synchrony during some periods of meditation, 16 increased alpha induction in response to stimulation, 52 increased hemispheric laterality during task, 53 shorter latency and higher amplitude visual and auditory evoked potentials, 54-58 changes in brain stem evoked potentials, 59 faster recovery of the paired Hoffman reflex, 60 EEG coherence and synchrony in the alpha and theta bands, 16, 61-65 and a fivefold increase in plasma arginine vasopressin elevation. 66 See reviews by Jevning and colleagues 67 and Alexander and colleagues. 68

Studies have shown that TM is not a single state, but is a dynamic process with 'inward and outward strokes' of meditation. 69-72 In his original studies on the physiology of TM, Wallace presented individual data and pointed to a variety of patterns that occur. 69 Wallace showed that basal skin resistance and other parameters often rise and fall several times during the practice, corresponding to the meditator's current physical and psychological condition. During the ‘inward stroke’ of meditation the mind settles inward towards a state of complete inner silence, which is called transcendental consciousness or pure consciousness by the ancient Vedic tradition.73 Patanjali's Yoga Sutras describe it as "the state of least excitation of consciousness" (1.2). 74 The ‘outward stroke’ of meditation corresponds to increased mental activity and metabolic activity resulting from normalization of imbalances in the system. 72

Even the "inward stroke" of meditation is not adequately described by the relaxation response. Many scholars have noted that experiences of transcendental consciousness are universal, found in all cultures, in both religious and secular settings, although their interpretation varies according to the cultural contexts. 73, 75-81 For example, one meditator says of his first experience of the TM technique: "I began to drift down into deeper and deeper levels of relaxation, as if I were sinking into my chair. Then for some time, perhaps a minute or a few minutes, I experienced a silent, inner state of no thoughts, just pure awareness and nothing else; then again I became aware of my surroundings. It left me with a deep sense of ease, inner renewal and happiness" (p. 334). 77 TM practitioners variously describe their personal experiences of transcendental consciousness as: "unbounded awareness," "enormously great calm and peace," "timelessness," "blissful awareness," "a balanced state of fulfillment that just is" (pp. 1571-1576). 82

Since Benson and colleagues refer to experiences of transcendental consciousness gleaned from the popular literature as evidence of the relaxation response, 1, 4, 5 it is important to note that the psychophysiology of transcendental consciousness is not adequately described by the relaxation response. Whereas during transcendental consciousness respiration rate is abruptly reduced by 40% or even suspended for up to a minute without compensatory breathing afterwards, 70-72, 82 skin conductance, an unambiguous marker of sympathetic nervous system activity, increases at the onset of the experience. 72 Other changes not predicted by the relaxation response include increased EEG power and coherence in the 6-10 Hz band, with large individual differences in peak frequencies and scalp locations. 64, 72

Meditative Prayer
Transcendental consciousness is the goal of some traditional meditation techniques, and the subjective descriptions of it from these traditions sound very similar to experiences of transcendental consciousness reported by TM meditators and from other secular sources. 79, 80, 83 William James, "the father of American psychology," collected these experiences and attempted to classify them, 75 but as yet objective evidence demonstrating their physiological effects is lacking.

In principle, however, religious or secular techniques that involve concentration or contemplation can not produce transcendental consciousness, because contemplation on the meaning of something or concentration on a single object of attention only create more mental activity, which is counterproductive to achieving inner silence. It is unlikely that relaxation techniques derived in clinical settings with the goal of relaxing the patient from an abnormally stressed and agitated state to a more or less ‘normal’ level of stress would produce transcendental consciousness, and no reports of this were found in the literature on the relaxation response or the Benson technique.


Part II: Comparisons of the Medical, Behavioral, and
Psychological Effects of Different Techniques

Soon after the relaxation response was proposed, Davidson and Schwartz proposed an alternative hypothesis that different meditation and relaxation techniques have specific effects: cognitive effects for cognitively oriented methods, autonomic effects for autonomically oriented methods. 84 Lehrer of the Robert Wood Johnson Medical School in New Jersey and colleagues published a qualitative review of 175 studies and 25 reviews that strongly supports the hypothesis of heterogeneous effects. 85 They found that electromyographic (EMG) biofeedback reduces muscle tension, whereas blood pressure biofeedback may modify blood pressure, and finger-temperature biofeedback may change peripheral circulation. Different techniques that target the same bodily system may have different effects on that system. Progressive muscle relaxation leads to generalized muscle relaxation, whereas for most people EMG biofeedback reduces tension only in the muscles to which feedback training is applied. Muscle relaxation and EMG biofeedback have smaller autonomic effects than finger temperature biofeedback and autogenic training, which involves visualizing pleasant past experiences. Autogenic training appears to have generalized autonomic effects that differ from the specific autonomic effects of biofeedback on heart rate, skin resistance, or blood pressure.

The cognitive activity required by autogenic training and hypnosis both involve suggestion, which is different from the activity required by meditation and cognitively-oriented techniques. The effects of EMG biofeedback on reducing stress through reducing muscle tension differ from those of the TM technique, which appears more effective at reversing endocrine changes due to chronic stress. 86 Lehrer and colleagues conclude that predominantly muscular disorders are best treated with muscularly oriented methods, while autonomic dysfunction such as hypertension and migraine headaches are more effectively treated with techniques that target the autonomic nervous system. Anxiety and phobias may be most effectively treated with methods that have both strong behavioral and cognitive components. Whether or not these generalizations are upheld by future research, there is now ample evidence that different techniques have specific effects and are not equivalent.

A meta-analysis by Hyman of the Albert Einstein College of Medicine of Yeshiva University in New York and colleagues of 48 studies on the effects of relaxation training and clinical symptoms found that effect sizes (standard deviation units) ranged ten fold, from .1 (very weak effect) to 1.11 (strong effect) and they state: "All treatments included in the analysis except Benson's relaxation technique demonstrated evidence of effectiveness" (p. 216) 10

Relaxation therapy and hypertension
Hypertension has been the most studied of stress-related disorders that the relaxation response is proposed to help. Yet meta-analyses have consistently shown that relaxation, hypnosis, and many meditation and stress management techniques do not have an effect on reducing blood pressure in hypertensive patients when design issues such as number of baseline measurements, familiarity with the measurement environment, and expectancy or placebo are taken into account. 87, 88 Benson is reported to have responded by saying that the relaxation response is effective for patients whose initial blood pressure is highest or whose hypertension is clearly linked to mental stress. 89

However, the meta-analysis by Jacobs of the University of Pittsburgh School of Medicine and colleagues took pre treatment pressure into account, as well as placebo, the number of baseline visits and the patients' familiarity with the clinical environment where blood pressure was measured. Relaxation therapy had little effect on reducing blood pressure that could not be accounted for by regression towards the mean, habituation, and placebo. In addition, techniques that are supposed to produce the relaxation response did particularly poorly. 88 With regard to mental stress, there is no clear indication that mentally stressed hypertensive patients will respond effectively to relaxation. Whereas some studies have found an association between pre-treatment anxiety levels and response to behavioral treatment, 90, 91 other studies found that lower levels of anxiety and hostility were associated with better treatment response. 88, 92, 93

A more recent randomized clinical trial of 127 elderly African Americans, compared TM, Progressive Relaxation (PR), and a diet exercise control (DE), 94, 95 matching groups on expectation of positive outcomes and keeping antihypertensive medication constant. Baseline measurements were taken over four visits, and program structure, time with the teacher, teacher motivation, subjects' evaluation of teacher's effectiveness, and other design features were equivalent between groups. In three months, TM reduced blood pressure by 10.7/6.4 mm Hg (comparable to anti-hypertensive medication), significantly more than PR or DE. PR also produced significant reductions compared to DE, but only half the reduction of the TM technique, supporting the view that different techniques have heterogeneous effects.

The study also found that TM was effective in reducing blood pressure in high and low risk groups on six measures of hypertension risk: psychosocial stress, obesity, alcohol use, physical inactivity, dietary sodium-potassium ratio, and a composite measure, 96 which is not in accord with Benson's assertion that the relaxation response works only (or works best) for patients with high stress levels.

Another random assignment study of blood pressure in the elderly that controlled for program structure and expectation fostering features found that TM produced significantly greater reductions in blood pressure than either the Benson technique (repetition of a well know phrase with a passive attitude towards thoughts) or mindfulness meditation. TM also produced a number of other positive benefits compared to the other two techniques, including increased longevity, increased cognitive flexibility, improvements in self-reported measures of behavioral flexibility and aging, and a greater sense of well-being and improved mental health. 97

Five and 15 year follow-up studies of these two randomized clinical blood pressure trials, respectively, found that TM significantly reduced cardiovascular and all-cause mortality compared to progressive relaxation, mindfulness meditation, the Benson technique, or a diet-exercise education program. 96, 98 TM subjects also had reduced Medicaid payments compared to subjects receiving progressive relaxation or the diet-exercise education program, 99 supporting previous research that TM reduces medical utilization and costs. 99-101

One possible mechanism by which TM reduces cardiovascular disease is that it appears to reduce lipid peroxide levels, controlling for smoking, fat intake, or vitamin supplementation, since oxidative stress (free radical activity) contributes to atheroscelerosis and aging. 102

Troubling Matters
Irwin Tessman of Purdue University and Jack Tessman of Tufts University found a number of discrepancies between Benson's claims for the relaxation response and the published data. In his book The Power and Biology of Belief , Benson cites a study on conception that he co-authored: "Thirty-six percent of women with unexpected infertility became pregnant within six months of completing the program [of the relaxation response]." The Tessman's found: "Unfortunately, perusal of the cited paper 103 reveals that there was no evidence that the relaxation response improved the conception rate, as the authors are careful to point out" (p. 369). 104 Finding a useful control, the Tessmans estimated that the fertility rate of women before they received the behavioral treatment "was at least equal to and possibly higher than the rate after treatment began" (p. 369).

In another example, the Tessmans wrote: "Another reported benefit of the relaxation response is that 'Patients who had open heart surgery had fewer postoperative arrhythmias and less anxiety following surgery.' However, the original study 105 demonstrated no significant evidence of benefits" (p. 369). 104

Five months later, in response to an article on the relaxation response appearing in Time magazine, 106 the Tessmans wrote a letter to Science . 107 In the Time article, Benson was quoted as saying that the relaxation response is clinically beneficial for insomnia, infertility, and chronic pain, e.g., "34% of chronic pain sufferers reduce their use of pain killing drugs." Looking into the original research, the Tessmans found: "Concerning insomnia, the relevant paper explicitly states that it is not possible to say whether the relaxation response contributes to therapy, because a multifactor approach was used. In a separate study involving small numbers of patients (10 test versus 10 control) and labeled as 'preliminary,' evidence of a small contribution of the relaxation response is made problematic by large standard errors of the means. Concerning infertility, the relevant paper disavows Benson's claim. Concerning chronic pain, again the relevant paper explicitly states that it is not possible to say whether the relaxation response contributes to therapy because they used a multifactor approach. And nothing at all is said about any reduction in the use of pain killing drugs." 107

In his letter of response, Benson wrote: "A lay magazine such as Time cannot always publish comments with the attention to detail that one would like." (p. 1694). 108 But he did not address the discrepancies between the published statements in his popular book and the published research reports, several which he co-authored. He writes in his letter: "It is the data published in the peer reviewed journals that I stand by" 108 and he quotes a list of results which appeared in a brochure for a continuing medical education seminar on "Spirituality and Healing" in Medicine II stating that the relaxation response is "an effective therapy for a number of diseases that include hypertension, cardiac rhythm irregularities, many forms of chronic pain, insomnia, infertility, the symptoms of cancer and AIDS, premenstrual syndrome, anxiety, and mild and moderate depression." 108 Benson writes of this list: "I also stand by these statements." But the Tessmans found that claims that the relaxation response is "an effective therapy" is simply not supported for infertility, cardiac rhythm irregularities, insomnia, and chronic pain. The meta-analyses reviewed above also invalidate hypertension.

With regard to chronic pain, Benson replies in his letter that an NIH Technology Assessment Conference concluded: "A number of well-defined behavioral and relaxation interventions now exist and are effective in the treatment of chronic pain and insomnia." 108 However, the Benson technique was not among the techniques found to work for chronic pain and insomnia. I was the reviewer for meditation techniques for that conference, 109 and I found three studies on the Benson technique. A study on pain after skin surgery did not find any differences from controls on a pain-rating scale, blood pressure, a symptoms index, or state-trait anxiety. The experimental subjects subjectively reported being helped, but details are not given in the paper on how this was measured. Moreover, experimental subjects received more local anesthetic than controls, which may have influenced their reports. 110 Similar results were found in a study using the Benson technique in combination with other relaxation techniques for post-operative distress in cholecystemy patients. This study did not find any changes in perceived pain intensity, abdominal EMG, or use of anesthetics, but patients did report being less distressed compared to controls receiving standard post-operative instructions. 111 A study of laboratory induced pain found that the Benson technique and controls sitting with eyes closed “engaging in any pleasant mental activity” did not differ from each other on pain sensitivity. This study concluded that there were no unique effects of Benson’s technique on pain compared to just ordinary sitting eyes closed. 112

With regard to premenstrual syndrome, the relevant study can only be viewed as very preliminary evidence, 113 because out of the initial 107 subjects, the study ended up with only 16 subjects in the relaxation response group, and change was found on only one of five measures. In addition, only seven "high severity subjects" improved relative to controls on some retrospective measures, and the authors suggest: "Such a differential effect of initial severity is most likely explained by a floor effect, because women with less severe symptoms have less opportunity for improvement than do women with relatively severe symptoms" (p. 653). However, the study had already eliminated 30 subjects because they did not meet a high enough threshold symptom severity to be included.

Regarding anxiety, a meta-analysis of 146 meditation and relaxation studies by Eppley of Stanford University and colleagues found that the Benson technique did no better than a placebo in reducing anxiety and that TM produced a significantly greater reduction in trait anxiety than other meditation or relaxation techniques, controlling for type of population, age, gender, quality of experimental design, duration and hours of treatment, pretest anxiety, demand characteristics, experimenter attitude, type of publication, and attrition. 12 A criticism of this meta-analysis argued that the TM subjects practiced the technique more frequently than the other groups (p. 235), 114 but Table 3 of the meta-analysis showed that there was no correlation between frequency of practice and effect size for all relaxation techniques or for other meditation techniques. In addition, for studies of other meditations in which the subjects practiced their techniques with the same frequency as did the TM subjects, the effect size was only .24, compared to .7 for TM (Table 1).

Meta-analyses on Substance Abuse and Mental Health
A meta-analysis of 198 studies on drug, alcohol, and tobacco consumption, covering subjects ranging from the general population to incarcerated drug offenders, compared relaxation techniques, therapeutic probation, pharmacological intervention, educational programs, and unconventional treatments (e.g., acupuncture), and TM. 115 TM studies showed substantially larger effect sizes in reducing consumption than other programs and showed that abstinence was maintained longer, controlling for research design strength and duration of practice.

A carefully controlled random assignment study of relapse prevention following alcoholism treatment in 'skid row alcoholics' found that 65% of the TM group and 55% of the EMG biofeedback group were completely abstinent after 18 months compared to 25 % abstinent for those receiving routine therapy or neurotherapy. 116 A wide range of evidence indicates that the physiological mechanism by which the TM technique affects substance abuse is normalization of the neurochemical imbalances. 47

A meta-analysis of 51 studies and 404 independent outcomes on positive and negative affect compared the Benson technique with meditation techniques (e.g.. Zen and TM), and found that TM consistently produced greater effect sizes when compared with other techniques. 117 Another meta-analysis of 42 independent outcomes found that the statistical effect size produced by TM on optimal psychological health (self-actualization) was three times larger than that produced by other forms of meditation and relaxation, controlling for duration of intervention and strength of experimental design. 118 A random assignment study of 83 black college students found that both TM and progressive relaxation significantly increased overall mental health and reduced anxiety compared to a cognitive-behavioral stategies group, and that TM showed greater reductions in neoroticism and increases in EEG coherence than the other groups. 65

Discussion
This review found that the physiological changes produced by different meditation and relaxation techniques are not accurately described by the relaxation response.11, 14, 18-23, 25, 28 The relaxation response was modeled on the changes produced by the Transcendental Meditation technique, 1-3, 6 yet some of the changes during TM are in the opposite direction of the relaxation response, 39-41, 72 while other changes are not predicted by it. 44, 45, 48, 50, 51, 59, 119, 120 Random assignment studies, meta-analyses and comprehensive reviews provide strong evidence that different meditation and relaxation techniques are not equivalent and that they have specific effects that are closely tied to their specific methodologies. 12, 38, 67, 68, 84, 85, 87, 88, 94-98, 115-118

This is not the first review to find evidence for the relaxation response lacking. In the 1980's the Chief of Medicine of Boston's Beth Hospital assembled an outside committee to evaluate Benson's work. Review panel member Bob Rose, a psychoendocrinologist, formerly on the editorial board of Psychosomatic Medicine, and currently director of health programs at the MacArthur Foundation said: "Herb has claimed to do the very basic kinds of biological research that document the psychobiogical mechanisms underlying the relaxation response, but it turns out that when you look very carefully that he hasn't done that"(p. 358). 89 In their letter to Science reviewed earlier, Irwin and Jack Tessman state: "We see Benson as a publicizer of therapeutic claims that appear not to be supported by the data." 107

Consequences
Over 4 million copies of the popular book on the relaxation response has been sold. 89 It is widely quoted in most textbooks and articles on meditation and relaxation techniques, and is often used as an interpretive framework of the medical benefits of different techniques. A search of the recent literature found that it is being used to explain the effects of progressive muscle relaxation, 121-123 hypnosis, 124, 125 biofeedback, 126, 127 shavasan yoga, 123 and the Broota technique. 123 This practice is not only an explanatory fiction, it inhibits useful research on the true mechanisms of these techniques. On the other hand, the practice of using the demonstrated effectiveness of different technique, such as TM or mindfulness meditation, 1-5, 35 as evidence for validity of the relaxation response is grossly misleading.

One can not assume that just because one technique has been shown to have a particular effect that all will have that effect. Nor does it follow that just because one or several techniques are shown not to be effective that all techniques are not effective. 128 For example, in 1992 a major NIH hypertension study of 2100 subjects did not find that relaxation (not including TM) was effective, whereas weight and sodium reduction were. Consequently, no relaxation technique was included in the larger phase II of the Trials for Hypertension Prevention. 89 More care in discriminating techniques that are effective from those that are not might have resulted in another outcome, that is, uncovering useful methods of preventing hypertension rather than discarding the whole notion of treating hypertension through stress reduction.

Relaxation therapies are now taught in 60% of medical schools, 89 with no distinction between those that work and those that do not, resulting in loss of cost effectiveness as well as promoting the unnecessary continuation of human suffering that could have been relieved by the application of effective technologies.

Acknowledgments
I wish to acknowledge librarian Jim Bates for all his help in obtaining reprints, and my wife, Dr. Rhoda Orme-Johnson, for her editorial assistance.

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