Background: In clinical studies there is a strong relationship between gastrointestinal symptoms, anxiety and depression. The results may be biased, however, since anxiety and depression will influence the decision to consult a doctor. The aim of this study was to investigate the relationship between these symptoms in the population.
Methods: In the Health Study of Nord-Trøndelag County of Norway (HUNT) a questionnaire concerning physical and mental health, demographic and life-style factors was sent to all inhabitants aged 20 years and above (a total of 94,197 persons). Valid questionnaires were returned by 62,651 persons (66.5%). Presence of nausea, heartburn, diarrhoea and constipation during the last year was self-reported. Anxiety disorders and depression were based on self-ratings of the Hospital Anxiety and Depression Scale (HADS).
Results: 48% of the population reported one or more of the four gastrointestinal symptoms. Based on the HADS ratings, 15.3% of the population had an anxiety disorder and 10.4% a depression. Anxiety disorder was most strongly associated with nausea (OR 3.42). Anxiety was also associated with heartburn, diarrhoea and constipation, but weaker than with nausea. Depression was less strongly associated with the four gastrointestinal symptoms. Demographic factors, life-style factors and extra-gastrointestinal complaints could not explain the effect of anxiety disorders and depression on these gastrointestinal symptoms.
Conclusions: In this population study there was a strong relationship between gastrointestinal symptoms, anxiety disorders and depression. These findings suggest that mental disorders in patients with gastrointestinal symptoms are not merely a consequence of selection bias in patient materials but connected to the symptoms themselves.