The relationship between stress and disease is now well established, but this was not always recognized. It was Hans Selye who first incorporated the term "stress" into the medical lexicon to describe the "nonspecific response of the body to any demand" . Selye, who is known as the 'father of stress research', disavowed the study of specific disease signs and symptoms, unlike others before him, and instead focused on universal patient reactions to illness. His concept of stress impacted scientific and lay communities alike, in fields as diverse as endocrinology, complementary medicine, animal breeding and social psychology.

 Selye pioneered investigations of the biological effects of stress in 1936 with the publication of his paper, "A syndrome produced by diverse noxious agents." Since then, more than 100,000 articles and books have been written on the subject. Selye describes stress as the nonspecific response to any demand. Although many individuals have concluded that stress is inevitably destructive, this view is incorrect. Selye noted: "Stress is not necessarily bad for you. It is also the spice of life, for any emotion, any activity causes stress ... the same stress that makes one person sick is invigorating experience for another ... Complete absence of stress is incompatible with life since only a dead man makes no demand on his body or

Selye described two types of stress: Dis-stress -­from the Latin "bad," as in dissonance, and Eu-stress from the Greek "true" or "good," as in eutonia. Whether we experience a pleasant or unpleasant result from an event depends upon how our nervous system perceives, processes, and interprets that event. More than 15 years before Selye's historic publication, B.J. Palmer, the Developer of Chiropractic and another chiropractor J.H. Craven described a similar concept: concussion of forces. This term refers to the meeting of external invasive forces and internal resistive forces. Just as stress may be destructive or beneficial, concussion of forces may produce or reduce vertebral subluxation. The result is dis-ease or ease.

Vertebral subluxations occur when the bones of the spine (vertebra) misalign, shift out of position and lose their normal motion. These spinal shifts can obstruct or irritate the nervous system and create a disconnect. They can also constantly send nerve energy that isn't needed through the system and cause facilitation. Because the nervous system controls and coordinates all functions in the body, obstructing, disconnecting or facilitating it can have an effect on every function of the body. Vertebral subluxations are what chiropractors correct.

Reference::
Christopher Kent, DC, JD. Chiropractic and Mental Health: History and Review of Putative Neurobiological Mechanisms. J. Philosophy, Principles & Practice of Chiropractic - August 30, 2018