Byline: Rahul. Kumar, Vikram. Yeragani
The interaction of Psyche and Soma are well known and this interaction happens through a complex network of feedback, medication, and modulation among the central and autonomic nervous systems, the endocrine system, the immune system, and the stress system. These systems, which were previously considered pristinely independent, in fact, interact at myriad levels. Psychoneuroimmunology (PNI) is an emerging discipline that focuses on various interactions among these body systems and provides the underpinnings of a scientific explanation for what is commonly referred to as the mind-body connection. This article reviews the relevant literature with an emphasis on Indian research.
Integral physiology has to do with the synthesis of conventional physiology and how our individual psyches (i.e., mind, emotions, and spirituality) interact with the world around us, to induce positive or detrimental changes in our bodies. In a broader sense, the concept applies to the health of society as a whole. In the past two decades, biomedical research has changed our understanding of body systems. It has now come to light that there is a complex network of feedback, mediation, and modulation among the central and autonomic nervous systems, the endocrine system, the immune system, and the stress system. These systems, which were previously considered pristinely independent, in fact, interact at myriad levels. Psychoneuroimmunology (PNI) is an emerging discipline that focuses on various interactions among these body systems and provides the underpinnings of a scientific explanation for what is commonly referred to as the mind-body connection. One should not construe here that all the phenomena are finally mediated only through immune mechanisms.
Emergence of PNI
In 1964, George Freeman Solomon wrote "Emotions, immunity, and disease: A speculative theoretical integration." In this article, Solomon first used the term ' psychoimmunology' and introduced the concept of a medical link between our emotions and immune systems. [sup] In 1975, Ader expanded on Solomon's work and coined the term ' PNI' . During that same year, Ader and his colleagues published the startling results of their research on the conditioned immune response in a rat population. [sup] The rats in the experimental group were injected with cyclophosphamide (an immunosuppressive agent), while simultaneously being given drinking water flavored with saccharin. The rats were later given only the saccharin-flavored water but no cyclophosphamide. To the researchers' surprise, the rats continued to evidence immunosuppression. This was the first documented example of Pavlovian conditioning of the immune response. In Ader's groundbreaking research, he used a pharmaceutical agent to induce the conditioned immune response. Subsequent studies have expanded on the theory to include investigations of conditioning stimuli that are neither physical nor chemical, but are instead cognitive (e.g, perceptions, thoughts, or emotional states). What has been discovered is that these cognitive stimuli can just as easily mediate changes in the immune system. Two noteworthy examples often quoted in the context of PNI are mentioned; one is that lymphocyte activity in men diminishes immediately after the death of a spouse from breast cancer, [sup] and second, a study of 75 medical students showed a significant reduction in natural killer-cell activity during the final examinations as compared to the previous month. [sup]
Twenty years later, Lancet published a study by Ader and Cohen that concludes with the following statement: "The association between stressful life experiences and changes in immune function do not establish a causal link between stress, immune function, and disease. This chain of events has not been definitively established". [sup] Thus, the unifying link remained elusive for a large part of the late twentieth century. Only recently have major breakthroughs occurred that have revolutionized our understanding of PNI. In this article, we will make an attempt to demonstrate the integration among body systems and also the causal link can now be established between these systems based on the available knowledge.
Conditioned Immune Response
The key phenomenon that is the basis for the discipline of PNI is the so called 'Conditioned Immune Response'. Research elucidating the interactions between the nervous and immune systems began with studies on conditioned responses of the immune system. As mentioned earlier, in 1975, Robert Ader and his colleagues published their research on the conditioned immune response in a rat population. Similarly, over a hundred years ago, Sir William Osler, the notable physician from John Hopkins, described a patient having an asthma attack after smelling an artificial rose. Although the effects of such conditioning were experientially familiar to physicians, Ader's experiment was the first scientific proof of Pavlovian conditioning of the immune response. Ader's research opened the way to a plethora of studies that …