The intention of this study was to evaluate therapy outcome of a cognitive-behavioral group treatment program for functional gastrointestinal disorders. As a particular characteristic, gastrointestinal symptoms were investigated independently from diagnostic categories on a dimensional basis, considering the persistence of symptoms as well as the aspect of severity.

A total of 64 subjects participated in the 10-week treatment program, and 49 completed the study. Subjects underwent four assessments (baseline, pre-, post-treatment, 12-month follow-up), each comprising several self-rated questionnaires on gastrointestinal, somatoform, depressive, hypochondriacal and anxious symptoms, and health locus of control, as well as a diagnostic interview of functional gastrointestinal and mental disorders at the baseline assessment. Treatment effects were controlled by subjects' waiting list period before treatment.

Gastrointestinal symptoms, as well as comorbid psychopathology scores, decreased significantly during treatment and remained unchanged during the follow-up period, whereas no relevant changes were found in health locus of control. Largest effect sizes were found for gastrointestinal symptoms, which decreased by 30–50% of their initial number.

The group treatment investigated was effective and particularly successful with respect to functional gastrointestinal symptoms. However, the mechanisms of treatment outcome remain indistinct. Further studies comparing different setting conditions directly are required to clarify the question of whether group treatment is significantly superior or inferior to individual therapy.