The PsychoNeuroEndocrineImmunology or PNEI is the study of the relationships among the major control systems of the human body: the nervous, the endocrine and the immune systems, and between them and the psyche which is the emotional and cognitive identity that distinguishes each of us.
The various systems (psychological, neurological, endocrine and immune) interact with each other to achieve an internal homeostasis of the organism. As a proof of this, it has been proved that the immune cells are able to interpret the messages coming from the autonomous nervous system (ANS) and from the brain.
If mind and body (Psyche and Soma) are therefore able to interact, it is not hard to accept the idea that the mood (meant as a frame of mind, more or less positive, at the interpretation of stimulus) may regulate, or at least influence (or if you prefer, interfere with) the central nervous system, the hormonal and immune ones.
Each emotional state as love, fear, pleasure, pain, anxiety, anger, etc., with its complex nuances commonly called feelings, is generated by processes that take place in the “noble” areas (cortex, limbic lobe, etc..) of the brain and spread throughout the body (and, therefore, in individual organs and systems) through a bioelectrical way (nerve neuronal and neuroglial impulses) and thanks to the operation of biochemical substances defined as “ligands” (which modulate the signal between the individual cells) , including neuropeptides, neurotransmitters and hormones.
These “ligands” and its receptors (specific “locks” located on the cell membrane) are present in every part of the body and not just in the nervous system. This means that the whole body “thinks” (even if in a more or less challenging way, depending on the specific area) and that each cell “feels” and tests “emotions”, creates its own information and sends them to every other cell through a dense communication network so each human psychophysical aspect may be seen as a part of a single reality.
The molecular basis of emotions can therefore be defined as the messengers that carry information to link the major body systems between them in a one functional unit that can be defined as the body / mind. The PNEI, represents that area of research that covers a wide range of scientific humanistic disciplines, and in the end, stands as a unifying mean for various aspects of the complex frame of the phenomena of adaptation of the organism.
The roots of the PNEI go back to the researches that were initiated in the 30’s of the last century by Hans Selye.
His studies brought him to develop a new theory about stress which synthesizes the works of two scientists, C. Bernard and W. Cannon who, to describe the functioning of the organism, introduced around 1920 the concepts of “steadiness of the internal environment”, of “homeostasis” and in particular of “stress”, to indicate an alarm reaction produced in the body by an external stimulus.
The concept of stress in medicine was shaped as an element of great importance recurrent in a large number of researches produced since the late nineteenth century, which suggested the influence of a variety of environmental stimuli in the relationship between hosting animal and pathogenic micro-organism and in the changing from the host susceptibility to infectious agents.
From Selye’s discoveries comes the current line of research about the relationship between physical and psychosocial stressors, nervous system, immune system and infectious diseases.
In the following seventy years many researchers have discussed, refined and changed his researches, but a new scientific horizon was deployed: the one of measuring, the objectification of the consequences that the action of external dangerous stimuli [stressor] has on the living body, harmful or lived as such.
It will be in the 70’s that they will get to prove that the brain, particularly the hypothalamus, activates the stress response and that it is always from the hypothalamus that other signals that rule the production of the main hormones leave: thyroid, sexual, growth, breastfeeding. During the same period Lazarus put a special attention on the psychological aspects involved in the stress response of men. Different people showed equally diverse biological responses to the same stimulus, especially if of low intensity and psycho-social.
It was then believed that, before inducing the emotional activation and then the stress reaction, the stimulus was processed through cognitive processes and rated [cognitive processing] in its characteristics and in its meaning from the CNS.
In the mid seventies Besedowsky showed that the stress reaction with the increasing of the production of cortisol by the adrenal, causes a suppression of the immune response.
The first biological link between the brain, stress and immunity was then set.
In the eighties, studies about the relationship between stress, brain and immunity increased. Various situations of psychological stress showed to change in the functionality of the immune system and many advances were achieved in the detection of the mediators and modulators of the immune response.
The 1981 with the work of Ader Psychoneuroimmunology, represents the birth, through a rigorous theoretical systematization, of Psychoneuroimmunology, that by broadening other developments in the endocrinological field will later be renamed Psychoneuroendocrineimmunology.
The neurophysiologist Candace Pert  studied the endorphins and a large number of neuropeptides, highlighting the role of mediators, not just of information but also of emotions and detecting the presence in all cells of the body.
Neuropeptides are considered molecules of the mind or of the emotions, because besides bringing hormonal and metabolic information they also bring emotions and psychophysical signals: because of them each emotional state is transmitted in the body [love, fear, pleasure, pain, anxiety, anger.
After this Pert proposes to change the term neuropeptides with that of peptides that seems more suitable to describe their role and functions.
This means that the whole body “thinks”, that every cell “feels”, “feels emotions,” receives psycho-physical information and transmits them to the entire organism through a dense network of interconnections of extreme communication variety, helping so to develop metabolic strategies for the global well-being.
his new theory the immune system is compared to a real sense organ, the inner eye which monitors both the exterior and the interior.
In the mind-body unity peptides and receptors represent the biochemical basis of emotions and it is therefore clear that emotions contribute to influence health and disease.
The outstanding innovation introduced by this model is not verifiable only for the implications in providing crisis of some principles of the traditional paradigm, but specially to confirm some important theoretical aspects present in non-conventional medicines that find explanations and feedback on the physiological and biochemical aspect.
Recent studies show that even pathologies such as atherosclerosis, traditionally conceived as the result of excess of cholesterol in the blood, are strongly influenced by the mood: depression, now considered an inflammatory disease, contributes to alter the inner wall of the vessels, facilitating the making of the typical atherosclerotic lesions.