"Researcher Hans Selye and others have discovered that over long periods of time stress depletes the body of energy, accelerates natural aging and the deterioration of the body. Diseases of premature aging and deterioration among others include: heart disease, cancer, high blood pressure, and musculoskeletal degeneration. Current opinion is that persistent unrelenting stress ages the body by distorting its normal physiologic balance. Much research has been done on the effect of stress on the function of the immune system. Steroids and other neuropeptide transmitters released by the brain at times of stress, appear to reduce immune surveillance, which is our own natural defense against infections agents and abnormal (cancerous) cells."
References - Hans Selye, Naomi O'Keefe Ph.D., CCH, Licensed Clinical Psychologist and Clinical Hypnotherapist
Taken From Clinical Hypnotherapy Doctorate Lecture 05/2004