Psychoneuroimmunology is the study of the interaction between the psychological processes of the body and the immune system. Because of its interdisciplinary nature, this field of study intersects with biology and psychology. Psychoneuroimmunology research has shown that stress is a significant underlying cause to many people’s day to day health problems, and has even shown that psychological treatment can lead to physiological health improvement.
The human immune system is affected by stress through emotional manifestations such as anxiety or fear, or physiological changes in blood pressure or heart rate. These changes can be useful in situations that cause stress for a short time, increasing our ability to move, think and react. When the stress becomes chronic these effects become detrimental to an individual's health. Research in psychoneuroimmunology has shown that long-term stress leads to an overall decrease of total white blood cells, and can be an underlying factor in many inflammation-related diseases such as rheumatoid arthritis.
The main process that causes this response to stress is called the immune-brain loop. Two main pathways are part of this loop: the Hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS). The HPA axis and SNS mediate the way hormones are released when stressed, increasing the production of stress hormones and other compounds that inhibit the effect of neurotransmitters such as serotonin, dopamine and other transmitters. When these transmitters are inhibited, it leads to a state of of neurohormone dysregulation. As a result of this, the body undergoes physiological changes such as inflammation and decreased immune response.