Research and clinical experiences show that people engaging in drug addiction for some years usually embrace severe mental illnesses including schizophrenia, borderline personality disorder, depression and post-traumatic stress disorder. Schizophrenia usually occurs in patients with prolonged use of amphetamine and hallucinogens. Borderline personality disorder commonly happens in female addicts who have experienced abandonment and childhood abuse. On the one hand, drug addiction can be used to cope with symptoms of severe mental illness. On the other hand, prolonged drug addiction can also induce severe mental illness. A close look into individuals with chronic drug addiction usually review that they encounter suffering, hardship and traumas. There are two types of traumas encountered by people with drug addiction. The first one is trauma before drug addiction and substance abuse. Many of them may have suffered through abuse, oppression and abandonment in their lives. Another one is drug led traumas because of psychosocial deprivation and medical problems induced by chronic addiction. In this book, apart from describing a comprehensive model in understanding and interpreting the complexity of trauma, mental illness and drug addiction, this model is applied and illustrated in clients with borderline personality disorder and schizophrenia, drug addiction and those who have experience different forms of trauma. Related psychosocial interventions are also thoroughly discussed.