Prof. J.P.N. Mishra
Based upon the metabolic characteristics of meditation and the subjective reports of meditators, several studies were initiated in order to ascertain whether the blood levels of stress-related chemicals decreased during this practice. A number of endocrine reactions have been identified in the meditative response pattern, including reduced blood levels of lactate, Cortisol, and epinephrine (Wallace 1970, Sudsuang et al 1991). The reductions in these blood chemicals denote a state of decreased tension and anxiety. For example, the infusion of lactate can produce anxiety symptoms in normal subjects (Wallace et al 1971); the decrease in lactate concentration during and after meditation may explain the subjective feelings of wakeful relaxation. These studies further reveal that the reduction in stress- related chemicals persists into the post-meditation period. The most likely explanation of these results seems to be that the long-term practice of meditation develops a psychophysiological response of persistent decreased endocrine activity, thereby reducing sensitivity to stress. It has been recently demonstrated that meditation reduces sympathetic adrenergic receptor sensitivity, producing a decreased response to stressful situations (Mills et al 1990).
Meditation is associated with changes in the secretion and release of several pituitary hormones. The hormonal changes induced by meditation mimic the effects of the inhibitory neurotransmitter GABA. Elias and Wilson (1995) hypothesize that meditation produces its anxiolytic effects by promoting GABA action in specific areas of the brain, via a mechanism similar to the effects of synthetic anxiolytic and tranquilizing agents. Melatonin has been associated with a variety of biologic functions important in maintaining health and preventing disease, and the serum level of the adrenal androgen DHEA-S has also been associated with measures of health and stress. For example, an increased level of DHEA-S has been connected with a reduction in age-related disorders such as cardiovascular diseases and breast cancer. DHEA-S excretion also decreases in times of stress; since meditators have been shown to have an attenuated autonomic response to stressors (Orme-Johnson 1973), the higher DHEA-S levels found in during meditation may provide protection against stressor stimulation of the adrenal gland.
That the physical effects of meditation persist after the meditation period itself has ended is demonstrated by the fact that hypertension can be effectively controlled by meditation alone without the use of anti-hypertensive drugs (Schneider et al 1995). Meditation has also been shown to have long-term effects on the endocrine system (Werner et al 1986). Another recent study (Zamarra et al 1996) reveals that meditators have a general increased exercise tolerance and maximal cardiac workload as compared to non-meditators.
