The K-SADS-PL is a semi-structured diagnostic interview designed to assess current and past episodes of psychopathology in children and adolescents ages 6-18 according to DSM-III-R and DSM-IV criteria. It is clinician-friendly. Probes and objective criteria are provided to rate individual symptoms. It assesses a variety of diagnoses, including major depression, schizophrenia, agoraphobia, ADHD, and eating disorders. Additionally, the instrument has three sections pertaining to substance abuse (cigarette use, alcohol abuse, and substance abuse in general), as well as a supplement (supplement #5) that addresses current and past Substance Abuse. Other diagnostic supplement modules cover Affective Disorders, Psychotic Disorders, Anxiety Disorders, and Behavioral Disorders including bulimia, anorexia nervosa, and tic disorders. Its strength is in diagnosis of affective and anxiety disorders. As a semi-structured interview, the questions included in the instrument do not have to be recited verbatim but instead are meant to serve as prompts to the interviewer. The K-SADS-PL is administered by interviewing the parent(s) and the child involved, and then finally achieving summary ratings which include all sources of information (parent, child, school, chart and other). Administration time is estimated to be 35-45 minutes each for healthy control subjects and about 75 minutes each for psychiatric patients. For research studies, a single diagnostic module of the K-SADS may be used for multiple interviews of a patient during treatment to assess symptom change.