Interest in the mind-body connection has grown in recent years, with accumulating evidence showing that the gut microbiome can alter behavioral, neural, and psychological outcomes. This publication brings together a group of international experts who are investigating the microbiome and its potential to contribute to the causes and treatment of mental illness. The contributions are not aimed solely at specialists in clinical and experimental neuroscience. They cover a range of key topics, including the role of the microbiome in mental health and specific psychiatric disorders that occur across the lifespan, interactions with the immune system, diet, and pharmacological interventions. Furthermore, the microbial metabolite production and the potential for psychobiotic interventions that target the microbiome to improve mental health outcomes are discussed. This book is unique in its focus on the mechanisms and consequences of the activities of gut microorganisms in mental health and illness, providing expert insight into the current state of the art and important future directions for this emerging area of research. Additionally, it provides an excellent knowledge base for newcomers and a refresher for researchers and clinicians working in the fields of neuroscience, psychology, or psychiatry.