The influence of the two different light intensities duringthe daytime on the colon motility in patients with irritable bowel syndrome (IBS): a preliminary report

Irritable bowel syndrome (IBS) is the most frequent functional disorder of the gastrointestinal tract, with great economical impact. The etiology and pathogenesis of the disease are unclear. Among patients seeking medical attention for IBS, 70 - 90% have psychiatric co-morbidity, most commonly major depression. In this study we test the influence of bright light on colon motility and subjectively felt symptoms. Eight IBS patients participated in the experiment. The passage rate was evaluated twice for every person: (1) after three days of exposure to bright light -3000 lux (from 8:00 to 18:00), (2) after three days exposure to dim light -100 lux (from 8:00 to 18:00). The comparison of colonic time in IBS patients point to differences in the elimination of markers, depending on experimental light conditions. After bright light conditions a tendency is observed to slower elimination of markers in the IBS-diarrhoea patients, and to a quicker elimination in the IBS-constipated patients. According to subjective feeling, all IBS patients reported an improvement in bowel function and relief of pain after bright but not after dim light application. Results of this preliminary study suggest that phototherapy might be a valuable addition to the conventional treatment of IBS.