The difference in scores on the SF-36 between the meditating population and the general Australian population is substantial and wide ranging. The apparent positive differences between the sample of meditation practitioners and the national norms may be the result of confounding factors. In an attempt to control for this, and although somewhat limited by the nature of the Australian National Health Survey dataset, even when comparing the health scores of that portion of the population that does not consume tobacco (the only factor that the ABS dataset allowed us to control for) but has the same age profile as the meditators sample, the significant differences persisted.
George and colleagues noted in their discussion about the nature and quality of samples used in surveys and longitudinal studies of religious practices that more than half of the studies that address the relationship between religion and health are based on samples of older adults (60+ years of age) [22
]. Epidemiological study of religiosity and its relationship to health is currently dominated by a Western, Judeo-Christian perspective. George further noted that these kinds of studies are usually conducted within limited geographic regions within the USA and are thus potentially influenced by regional variations in religious observance (e.g., Bible Belt states versus West Coast). In contrast, this study involved a national, representative sample of meditators, the sample group was relatively young (with a mean age of 37), and its outcomes were compared to national, census-based normative data. An additional strength of this study is that it examined non-Judeo-Christian religiosity in a country comparable to, although not geographically connected to, the USA, on a sample of respondents who are ethnically similar and yet religiously different.
The meditator population may well be selected for those who are more motivated to achieve and maintain health. Various surveys have shown that people who use meditation and other forms of complementary and alternative medicine hold strong affiliations with holistic health philosophies and are highly motivated to seek out self-empowering health improvement strategies. It is quite possible that a population of long-term meditation practitioners would be highly selected for such people. Moreover, those practitioners who do not experience positive effects or even experience negative effects naturally desist from the practice and attrit from the meditating population, further improving the mean health scores of the remaining population.
Surveys of this nature necessarily generate a level of expectancy among respondents. The responses of the long-term meditating population could have been influenced by the prospect of the survey results constituting a validation of their chosen lifestyle and belief system. Nevertheless, the fact that the overall pattern of response in the meditating sample follows a similar pattern to that of the Australian population provides some reassurance that this was not a major confounder. Furthermore, the data reported here are almost exactly the same as the data obtained in two pilot surveys.
It is important to note that while modern science most commonly characterises meditation as a relaxation response or a pattern of specifically focused attention, these conceptualisations differ fundamentally from the authentic descriptions of the meditative experience originating in ancient India. The original source texts clearly state that a key defining feature of meditation is the experience of mental silence. For example, in what is probably the oldest known definition of meditation, the narrator explains in the ancient Indian Mahabharata that a meditator is “… like a log, he does not think” [23
]. Similarly Lao Tse instructs the reader in the Tao Te Ching to “empty the mind of all thoughts”. Many other explicit examples of this idea can be found in Eastern literature from virtually every historical period. Yet Western definitions of meditation have consistently failed to acknowledge this crucial feature.
The mechanisms by which meditation techniques exert their claimed effects are also unclear. One very popular view, which has become more or less the default explanation, is that the physiological changes are characterised by the relaxation response—that is, the physiological changes that occur during rest, characterised by reductions in heart rate, blood pressure, and respiratory rate and increases in skin temperature, skin resistance, and alpha wave activity in the brain are thought to be responsible. All of these are brought about by reducing activity of the sympathetic component of the autonomic nervous system and increasing activity of the parasympathetic components of the ANS. Psychophysiological studies of Sahaja Yoga, that is mental silence, however suggest that it does not elicit a typical relaxation response. For example, a study of skin temperature changes during a single Sahaja Yoga meditation session demonstrated a reduction in palmar skin temperature, which is the opposite of that predicted by the relaxation response model. A control group that was engaged in simple rest did manifest skin temperature increases. Yet there were no significant differences in heart rate between the two groups [24
In her 2001 study, Meisenhelder proposed that the relationships observed between frequency of prayer and higher health scores could at least be partly caused by the relaxation effect of prayer and its consequent ability to ameliorate the effects of stress. This idea is supported by studies such as that by Carlson who studied the autonomic impact of Christian devotional meditation in an RCT design and found that it was as effective, and in some parameters more effective, as conventional relaxation [25
So, it is noteworthy that both this study and the study by Meisenhelder and Chandler [1
] report correlations in the same SF-36 subscales (general health, vitality, and mental health) suggesting that both prayer and meditation are both associated with similareffects. An interesting distinction however is that our study suggests that the experience of mental silence has a stronger (by a factor of approximately two to three) relationship with these dimensions as compared to the relationship that Meisenhelder reports between prayer and the same dimensions. The notion that this may be due to some inherent effect of the mental silence experience is supported by the two RCTs on work stress and asthma, mentioned earlier, and clearly warrants further investigation.
The observed relationship between how often a meditator performed “formal meditation” and health measures was considerably weaker than for mental silence, implying that differences between contemplative practices (such as prayer or meditation) that are overtly similar but sometimes experientially distinct (i.e., mental silence versus mental activity) have significantly different health implications.
The observed relationship between meditative practices and mental health is not as strong as for measures of physical health. In many ways, this might be expected since the intervention is primarily focused on a mental experience with the specific aim of reducing negative affect, thinking patterns, and related behaviours. Mood, thoughts, and behaviour patterns are in constant flux, much of it reflecting (and influencing) brain electrochemical activity and other neurobehavioural phenomena which change from moment to moment.
There is evidence that meditation can have short- and long-term effects on both function and structural brain plasticity in addition to its already recognised ability to cause relaxation and reduce stress. Aftanas has shown that the practice of SYM, and the experience of mental silence, is strongly reflected in both brain electrophysiology and mood [26
]. A study by the same group demonstrated reduced emotional reactivity in long-term meditators compared to controls which was reflected in psychological, physiological, and electrophysiological reactivity to standardised stressful stimuli presented in a video film. This provides evidence for the notion of “emotional detachment” and hence enhanced emotional stability and resilience to stressful events [27
]. A smaller intervention study by Morgan over just 6 weeks showed a significant reduction in anxiety, depression, and related symptoms in patients with major depression compared to controls [17
] which appears to reflect the clinical relevance of Aftanas's findings. This has broader implications particularly as understandings of the relationship between neuroplasticity and meditation emerge. Lazar studied a group of Buddhist meditators and found that meditators compared to controls had significantly increased cortical thickness in right middle and superior frontal cortex and insula suggesting that meditation is associated with delaying of the usually age-related thinning of right frontolimbic brain regions [28
]. Hence it is quite possible that long-term meditation may facilitate both electrophysiological and structural changes in brain function that may explain why the population of long-term meditators that we studied manifested an apparent advantage as compared to the background population particularly in metal health scores. An excellent review and discussion paper by Rubia [29
] discusses the possible neurobiological underpinnings of meditation and its potential role in mental health in detail that is not possible within the limits of this paper.
These observations might also explain why mental health factors are much more likely to be immediately responsive to such an intervention whereas physical health factors, which rely significantly on anatomical structures and mechanical function, will take much longer to manifest (if at all) and are subject to a vast number of other environmental confounders that may obscure any such relationship.
While we acknowledge that cross-sectional studies are prone to a number of confounders, the implications for population mental health are nevertheless worth considering. Given that neuropsychiatric disorders such as depression and substance abuse are increasing in incidence as well as their impact and that there are few long-term curative options for many of these conditions, there is merit in exploring the role of preventative strategies such as meditation. The findings of this study warrant further examination of meditative practices as a conceptually innovative preventative and therapeutic option for public mental health. The meditation technique assessed in this study is low/zero cost and to date has not been associated with any adverse effects; hence further exploration of this approach in enhancing general wellbeing, quality of life, and mental health would seem to be highly worthwhile.