Now significantly revised with over 70% new material, this is the authoritative presentation of Internal Family Systems (IFS) therapy, which is taught and practiced around the world. IFS reveals how the subpersonalities or "parts" of each individual's psyche relate to each other like members of a family, and how--just as in a family--polarization among parts can lead to emotional suffering. IFS originator Richard Schwartz and master clinician Martha Sweezy explain core concepts and provide practical guidelines for implementing IFS with clients who are struggling with trauma, anxiety, depression, eating disorders, addiction, and other behavioral problems. They also address strategies for treating families and couples. IFS therapy is listed in SAMHSA's National Registry of Evidence-Based Programs and Practices.