ReviewThe neurobiology of Meditation and its clinical effectiveness in psychiatric disorders
Introduction
Neuropsychiatric disorders such as depression, alcohol and drug abuse are on the increase worldwide. Neuropsychiatric disorders account for 31% of total disability and are expected to rise by 2020 (Mathers and Loncar, 2005). Depression is the most common of all mental disorders with the greatest public health burden. According to estimates from the World Health Organisation (WHO) by 2020 depression will be the leading cause for disability worldwide. Suicide is estimated to be the leading cause of death in young people in 2020 (Mathers and Loncar, 2005). There have been increases in the number of diagnoses of mental health problems including schizophrenia, dementia, alcohol and substance abuse, and most child psychiatric disorders, which in part may be confounded by better detection, improved services and diagnostic changes. Nevertheless, these will be an increasing part of the overall health burden in the future.
Currently, there is no long-term cure of mental illness. Conventional behavioural or pharmacological treatment, though not a cure, has shown effectiveness in the alleviation of symptoms. However, dissatisfaction has arisen with psychopharmacological interventions due to side effects, its escalating prescription rates in both adults and children, and recent uncertainties on the effectiveness and long-term benefits of some psychopharmacological treatments such as antidepressants and psychostimulants (Jensen et al., 2007, Kirsch et al., 2008). Innovative conceptual and therapeutic models of care continue to emerge that may be relevant to the amelioration of mental illness. One of these is Meditation. Meditation has in recent years received considerable attention as a potential adjunct or alone in the intervention of psychiatric disorders as it is cost-effective and presumably free of side effects. In this paper we discuss the physiological and neurophysiological underpinnings of the subjectively reported benefits of Meditation and its potential effectiveness as a complementary treatment approach for mental illness.
Section snippets
What is Meditation and why could it be a useful adjunct to achieve mental health?
Meditation is essentially a physiological state of demonstrated reduced metabolic activity – different from sleep – that elicits physical and mental relaxation and is reported to enhance psychological balance and emotional stability (Jevning et al., 1992, Young and Taylor, 2001). In Western psychology, three states of consciousness are described: sleep, dream and wakefulness. In Eastern philosophy and in several Western religious and mystical traditions, an additional and supposedly “higher”
Peripheral physiological changes during Meditation
Studies comparing experienced Meditators compared to controls or short-term Meditators have demonstrated physiological changes during Meditation suggestive of a wakeful hypometabolic state that is characterised by decreased sympathetic nervous activity, important for fight and flight mechanisms, and increased parasympathetic activity, important for relaxation and rest (Cahn and Polich, 2006, Jevning et al., 1992, Rai et al., 1988, Young and Taylor, 2001). This wakeful hypometabolic state with
Neurophysiological effects during Meditation
As mentioned before, the key subjective experiences in Meditation, apart from a general relaxation response, are the reduction of mental activity and the generation of positive affect. Functional neuroimaging studies have in fact been able to corroborate these subjective experiences by demonstrating the up-regulation in brain regions of internalised attention and emotion processing with Meditation.
Many electrophysiological studies have examined the brain activation during a variety of
Evidence for long-term benefits of Meditation
The majority of Meditation studies have investigated the physiological and neurobiological correlates of the acute effects of Meditation. Clinically more interesting, however, is whether Meditation has sustainable effects on cognitive functions, brain plasticity and mental health. Very few studies have provided evidence for long-term, sustainable effects.
Evidence exists for long-term improvements with Meditation in cognitive skills, mainly in the domains of attention, inhibitory control and
Specificity of the neural substrates of Meditation compared to relaxation
It has been argued that Meditation is not different from simple relaxation. And there are certainly some Meditation techniques that do not claim to go beyond relaxation. Nevertheless, one would expect the neurobiology of the more concentrative Meditation techniques to differ from that of general relaxation, given that in addition to relaxing the body these “cognitive relaxation” techniques aim at reducing mental activity, hence also relaxing the mind. Mental relaxation, in turn, may feedback to
Clinical effectiveness of Meditation in psychiatric disorders
Given the preliminary but growing evidence for short and long-term effects of Meditation on physiological indicators of stress, on personality and cognitive functions, and on functional and structural plasticity of brain regions that are important for attention and emotion regulation, mental disorders, typically characterized by affective and cognitive-attentional problems, are an obvious target to study the clinical effects of Meditation.
Research of the clinical application of Meditation
Overall conclusions
Several Meditation techniques appear to have short and long-term effects on functional and structural brain plasticity as well as on physiological indicators of relaxation and stress relief. There is evidence to suggest that these effects are specific to Meditation over and above simple relaxation effects. There is furthermore preliminary evidence for enhanced psycho-emotional balance and focussed attention skills in long-term Meditators. The up-regulating functional effects on fronto-parietal
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