New research suggests that mental disorders and physical diseases co-occur more often than the average in teenagers.

Researchers at the University of Basel and the Ruhr-Universität Bochum found that more than a third of children and adolescents have suffered from one mental disorder and one physical disease.

Depression occurs together with diseases of the digestive system, eating disorders with seizures and anxiety disorders together with arthritis, heart disease as well as diseases of the digestives system.

For the study, researchers collected and analyzed data from nearly 6,500 teenagers in the United States.

They found that 35.3 percent of children and adolescents reported at least one mental disorder and one chronic physical disease. The strongest correlation was found between affective disorders (e.g. depression) and diseases of the digestive system.

Adolescents with anxiety disorders were also suffering above-average from arthritis, heart disease and diseases of the digestive system. Similar correlations occurred between eating disorders and seizures (epilepsy). Factors such as age, gender or socioeconomic status of the adolescents did not account for these associations.

Researchers said that due to the cross-sectional design of the study, the results do not show if and how mental disorders and physical disease are also connected causally.

"Future studies should identify risk factors as well as the biological and psychological mechanisms responsible for these associations, in order to develop interdisciplinary approaches," explained Maion Tegethoff, first author of the study.

The findings are detailed in the journal Psychosomatic Medicine.