The direct impact of negative thoughts and emotions on immunological function seems to be reasonably well documented and, since many Psychoneuroimmunology (PNI) phenomena seem to be mediated by negative affect, rather than situational “stress”, strategies that directly modify this factor may manifest greater benefits. While relaxation orientated meditation most likely acts to reduce the impact of stress that are mediated by neuroendocrine mechanisms such as the sympathoadrenal and hypothalamicpituitary axes, so too do other strategies that reduce physiological arousal. It might be argued that since mental silence approaches to meditation aim to not only reduce physiological arousal but also mitigate negative rumination and affect this may be one reason why it seems to be associated with a specific effect.
For more information on the effect a negative mood can have on the immune system, check out Dr Ramesh Manocha’s article on Psychoneuroimmunology.