Obesity and mental illness are two of the largest health issues the United States is currently facing, and their burden to society in human suffering, health care costs, and lost productivity is immense. The known psychosocial consequences of obesity include reduced educational attainment and lower rates of marriage. In adults presenting for the treatment of obesity, co-morbid psychopathology is increased. Widespread stigmatization of obese children is manifested through teasing and increased social stress. Nonetheless, the epidemiology of psychological outcomes subsequent to obesity has not been well characterized, and associations between obesity and psychopathology have frequently been assessed in clinical samples, or have used cross-sectional study designs. The proposed analyses make use of comprehensive data, from a longitudinal community study of determinants of psychological health from childhood to early adulthood, to characterize the specific psychological consequences of obesity and associations with relative weight during adolescence, and to assess the role of psychopathology on the development of obesity. Psychopathology is assessed based on standard Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic criteria as well as by symptom scales. With longitudinal statistical modeling, the bi-directional associations of adolescent relative weight with anxiety disorders, mood disorders, and overall psychopathology will be assessed. The extent to which mediating and moderating factors contribute to the development of adolescent obesity and influence subsequent psychopathology will be examined. Relative weight will be assessed based on body mass index (BMI) calculated from self-reported height and weight. The Centers for Disease Control's BMI growth reference will be used to determine age- and sex-specific BMI z-scores. Obesity will be defined as a BMI score above the 85th percentile from the CDC growth reference. Understanding the psychological consequences of obesity will allow for increasingly focused research in prevention and treatment efforts aimed at reducing psychological and physical suffering from obesity and from mental illness.