Health psychology developed in different forms in different societies. Psychological factors in health had been studied since the early 20th century by disciplines such as psychosomatic medicine and later behavioral medicine, but these were primarily branches of medicine, not psychology.

United States In 1969, William Schofield prepared a report for the APA entitled The Role of Psychology in the Delivery of Health Services. While there were exceptions, he found that the psychological research of the time frequently regarded mental health and physical health as separate, and devoted very little attention to psychology's impact upon physical health. One of the few psychologists working in this area at the time, Schofield proposed new forms of education and training for future psychologists. The APA, responding to his proposal, in 1973 established a task force to consider how psychologists could (a) help people to manage their health-related behaviors, (b) help patients manage their physical health problems, and (c) train healthcare staff to work more effectively with patients.

Health psychology began to emerge as a distinct discipline of psychology in the United States in the 1970s. In the mid-20th century there was a growing understanding in medicine of the effect of behavior on health. For example, the Alameda County Study, which began in the 1960s, showed that people who ate regular meals (e.g., breakfast), maintained a healthy weight, received adequate sleep, did not smoke, drank little alcohol, and exercised regularly were in better health and lived longer. In addition, psychologists and other scientists were discovering relationships between psychological processes and physiological ones. These discoveries include a better understanding of the impact of psychosocial stress on the cardiovascular and immune systems, and the early finding that the functioning of the immune system could be altered by learning.

Led by Joseph Matarazzo, in 1977, APA added a division devoted to health psychology. At the first divisional conference, Matarazzo delivered a speech that played an important role in defining health psychology. He defined the new field in this way, "Health psychology is the aggregate of the specific educational, scientific and professional contributions of the discipline of psychology to the promotion and maintenance of health, the prevention and treatment of illness, the identification of diagnostic and etiologic correlates of health, illness and related dysfunction, and the analysis and improvement of the healthcare system and health policy formation." In the 1980s, similar organizations were established elsewhere. In 1986, the BPS established a Division of Health Psychology. The European Health Psychology Society was also established in 1986. Similar organizations were established in other countries, including Australia and Japan. Universities began to develop doctoral level training programs in health psychology. In the US, post-doctoral level health psychology training programs were established for individuals who completed a doctoral degree in clinical psychology.

United Kingdom Psychologists have been working in medical settings for many years (in the UK sometimes the field was termed medical psychology). Medical psychology, however, was a relatively small field, primarily aimed at helping patients adjust to illness. The BPS's reconsideration of the role of the Medical Section prompted the emergence of health psychology as a distinct field. Marie Johnston and John Weinman argued in a letter to the BPS Bulletin that there was a great need for a Health Psychology Section. In December 1986 the section was established at the BPS London Conference, with Marie Johnston as chair. At the Annual BPS Conference in 1993 a review of "Current Trends in Health Psychology" was organized, and a definition of health psychology as "the study of psychological and behavioural processes in health, illness and healthcare" was proposed.

The Health Psychology Section became a Special Group in 1993 and was awarded divisional status within the UK in 1997. The awarding of divisional status meant that the individual training needs and professional practice of health psychologists were recognized, and members were able to obtain chartered status with the BPS. The BPS went on to regulate training and practice in health psychology until the regulation of professional standards and qualifications was taken over by statutory registration with the Health Professions Council in 2010.

A number of relevant trends coincided with the emergence of health psychology, including:

Epidemiological evidence linking behavior and health.

The addition of behavioral science to medical school curricula, with courses often taught by psychologists.

The training of health professionals in communication skills, with the aim of improving patient satisfaction and adherence to medical treatment.

Increasing numbers of interventions based on psychological theory (e.g., behavior modification).

An increased understanding of the interaction between psychological and physiological factors leading to the emergence of psychophysiology and psychoneuroimmunology (PNI).

The health domain having become a target of research by social psychologists interested in testing theoretical models linking beliefs, attitudes, and behavior.

The emergence of AIDS/HIV, and the increase in funding for behavioral research the epidemic provoked.

The emergence of academic /professional bodies to promote research and practice in health psychology was followed by the publication of a series of textbooks which began to lay out the interests of the discipline.

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Andrena Cindrella

Journal of Pschology & Psychotherapy