Are biology and psychology inseparable? For many decades, this notion was not seriously entertained by purveyors of psychological wisdom. Now, fast-growing new technologies for studying the brain have discredited the dichotomous biology-psychology divide, demonstrating that the foundations of psychology are based in neurobiological structures and functions, both inborn (temperament) and sometimes modified through interacting with environments. This book for social workers illustrates how social, psychological, and biological factors interact to shape a client's unique experience. While the field-and its longstanding texts-has for decades recognized the psychosocial elements that can help or hinder health and well being, it has been slow to integrate biological advances into its knowledge base. Synapse and System revolutionizes the way students learn to understand, assess, and treat their clients. Emphasizing the deep interconnectedness of genes and the physical and social context in which disorders take shape, this book introduces the fundamentals of neurochemistry and the biological roots of addiction, mental illness, trauma, attachment, and violence. In addition, it provides neuroscience fundamentals, incorporates new advances in neuroscience critical for practice, such as analysis and illustration of two examples of complex neural circuits, for pleasure and for trauma, and introduces many rich multidisciplinary research findings across practice areas. The result is a masterful treatment of social work's hallmark person-in-environment perspective that gives students a deep appreciation for the complex interactions among biological and social forces that can shape the development of, and response to, mental illness and social problems.