This book seeks to represent the main concepts and theories related to psychoneuroimmunology with the aim of their application in clinical settings and formation of novel theories to further elucidate the mutual connection of the psyche and the physiology of humans body. Psychoneuroimmunology, as an integration of popular research fields such as psychology, immunology, neurology, and neuroscience, is a perfect example of interdisciplinary and transdisciplinary studies that could potentially result in developing alternative diagnostic tools and treatment strategies besides facilitating the understanding of the pathophysiology of some conditions that might not properly be understood with a single point of view. Considering the stressful lifestyle and the high prevalence of neuropsychiatric, metabolic, and immune-related disorders, psychoneuroimmunology could be the path to the management of these conditions and reduction of the burden of the diseases