There have been remarkably few studies into levels of mental-health problems among teenagers using official diagnostic criteria. Researchers from Texas University studied 3,154 children (between the ages of 11 and 17) and their parents over the course of a year. They found that 2.8% had anxiety, 1.5% mood disorders, 1.2% attention-deficit hyperactivity disorder (ADHD), 2.5% disruptive disorder, 2.9% substance abuse/dependence and 7.5% one or more mental-health problems. The most consistent factor in predicting mental-health problems was levels of stress with family problems being particularly important. The presence of more than one risk factor substantially increased the chances of developing a mental-health problem while personal qualities such as mastery protected against them.
Roberts, Robert E., Roberts, Catherine R. and Chan, Wenyaw - One-year incidence of psychiatric disorders and associated risk factors among adolescents in the community Journal of Child Psychology and Psychiatry April 2009, 50(4), 405-415