This book presents information about brain function and its chemical underpinnings in a way that contributes to a conceptual understanding of distress and subjective well-being. Chapter 1 of the book provides a history of thought in psychiatry and explains how we arrived at our current system for categorizing distress. The second chapter offers information on physiology, including brain circuits undergirding anxiety and depression, circuits for emotional or impulse regulation, and circuits for robust motivated behaviors. Information on pharmacology, including the major classes of drugs used to influence behaviour, and the issues over the regulation of pharmaceuticals are presented in the third chapter. This is followed by five chapters that consider categories of distress that afflict adults, namely, depression, anxiety disorders, psychotic disorders, bipolar disorders and addictions. Chapter 9 focuses on categories of distress in children such as pediatric bipolar disorder and depression. The last chapter of the book considers whether current diagnostic practices have served us well, looks at an alternative focus for delivering mental health services, and deals with those behaviors that promote flourishing and well-being.