Book excerpt: The editor and authors of Youth Substance Abuse and Co-occurring Disorders take an applied approach that serves the needs of clinicians, clinical researchers, and students in the fields of mental health, public health, and medicine (pediatrics, family medicine, and child and adolescent psychiatry, in particular). While the population of adolescents with SUD possesses diverse clinical characteristics, 70%--80% manifest comorbid psychopathology, known also as co-occurring disorders or dual diagnosis -- that is, the presence of one or more comorbid psychiatric disorders in addition to SUDs. These comorbidities can greatly complicate assessment and treatment, and this book provides clinicians with not only the theory behind the various approaches to SUD but also the practical knowledge that is essential to understand and treat psychiatric comorbidity in these adolescents. Some of the most prominent investigators in the field have contributed scholarly chapters to the volume, which offers a multitude of useful features: An extensive examination of the etiology of SUD, focusing on whether psychopathology may precede SUD, as in the majority of cases, develop as a consequence of preexisting SUD, or originate from a common vulnerability Consistent emphasis on future directions in clinical research and treatment advancement, which helps the reader identify critical gaps in understanding the relationship between SUD and psychiatric comorbidity among youth Thorough, state-of-the art chapters on the developmental pathways and relationships between substance use and co-occurring psychiatric disorders, screening tools and interventions, and the full range of co-occurring disorders make the book ideal for instructional use Information on risk factors for development of SUD in adolescence, including psychiatric disorders in childhood such as disruptive behavior disorders, mood, anxiety disorders, etc. Clinically useful and scientifically rigorous, Youth Substance Abuse and Co-occurring Disorders should stimulate further discussion and advancement of the field, ultimately resulting in improved and more effective services and intervention modalities for these youth.