The theory of “general adaptation syndrome” proposed in 1936 relates stress with cortico-adrenal secretion and accounts for the protective effects of adrenal extracts on stress . Subsequently, Solomon et al., introduced a “speculative theory”, later known as psychoimmunology, and following the introduction of this theory, Ader and Cohen published their work on classical conditioning of immune functions entitled “Behavioral conditioning of immunosuppression”, in which they proposed a functional link between the immune system and the nervous system such that the immune response generates cytokines that stimulate the CNS [6, 7]. This stimulation of the brain activates the hypothalamic-pituitary-adrenal axis, which in turn suppresses the immune response through the secretion of glucocorticoids . Accumulating evidence since 1980 has established the mechanism by which thoughts, emotions and behavior modulate and mediate endocrine and immune functions .