Doctors of chiropractic analyze your spine to locate a vertebral subluxation (nerve pressure), a serious condition that causes spinal distortion and interferes with your nervous system function. Over a hundred years of chiropractic and osteopathic observations have demonstrated to many patients that spinal care improves immune function.^{1 2 3 4} The exact mechanism of how the spine and the nervous system affects the immune system is one of the hottest areas of scientific inquiry. This new field is called psychoneuroimmunology.⁵

A depressed person has a depressed immune system; a happy person has a healthier one. Bernie S. Siegel, M.D. has noted that unexpressed feelings depress immune response.⁶ In 1982, two Harvard psychologists, David McClelland and Carol Kirshnit, found that simply watching movies about love increases the level of immunoglobulin-A, a defense against colds and other viral diseases. According to Leo Buscaglia, insurance companies have found that if a wife kisses her husband good-bye in the morning he has fewer auto accidents and lives five years longer.

Companionship is one of the most effective means of coping with and reducing emotional stress. NASA research has shown that married astronauts were more stable emotionally than their single counterparts. Furthermore, recent research indicates that having a pet helps one to combat stress; studies show that dog owners have less stress because of the calming effect of their pets. Elderly pet owners visited doctors less than their same-aged counterparts who had no pets. ^{7 8}

A person under intense psychological stress is more likely to have a weakened immune system.⁹ In a 1988 study, students were divided into three groups: one worked crossword puzzles, one was given relaxation training, an one received relaxation and visual imagery training in which they pictured their powerful and strong immune systems attaching weak flu and cold viruses. Group one showed no increase in immune cells; group two showed a slight increase; group three showed a significant increase after only one hour of training. ¹⁰