The practice of treating children and adolescents for emotional and behavioral problems is at least a century old. In its early years, at the turn of the twentieth century, youth treatment was a rarity, but in recent decades the practice has surged in scope and cost to become a major component of care for young people. Now, early in the twenty-first century, millions of girls and boys receive psychotherapy every year in countries and cultures around the world, and significant portions of many national budgets are devoted to the mental health care these young people receive. Youth psychotherapy is remarkably diverse in its forms and methods. Hundreds of schools of therapy are brought to bear by professionals in their work with young people, and many of these professionals are highly eclectic, drawing goals and methods from a broad array of sources and using their best judgment to help the youngsters they see.

The practice of testing the effects of youth psychotherapies, using clinical trials, is naturally much younger than the treatment tradition. And at any point in time, many more professionals are providing youth psychotherapy than conducting research to test it. However, like youth treatment, youth treatment research has surged in recent decades. Well over 1,500 studies of youth psychotherapy effects have been completed to date, and hundreds of these meet standards for inclusion in scientific reviews, including quantitative syntheses called meta-analyses. Emerging from this body of treatment outcome research is a growing number of specific treatments that have significant evidence in their support, replicated across studies. These evidence-based treatments reflect the interplay of clinical care and scientific scrutiny.