Introduction to the Volume: The Journey Ahead.

The endogenous opioid system (EOS) is complex. The line of research contributing to our current body of knowledge about this system is diverse, as are the ways in which endogenous opioids affect human health and behavior. This chapter serves as an introduction to the edited volume. It includes commentary about the current public discourse related to opioids, the rationale for this book, and the unique contributions of each chapter within this volume.