Objective — to assess the impact of emotional and mental stress, duration of sleep and bedtime on the occurrence of ulcerative colitis (UC) in the population of the Western Siberia. Material and methods. A retrospective case-control study included 81 patients with ulcerative colitis and 39 healthy respondents. Mental tension and stress severity prior to the diagnosis of ulcerative colitis were compared with the same variables in healthy respondents. Effect of sleep duration on the occurrence of ulcerative colitis was analyzed using a specific questionnaire to specify bedtime and duration of sleep. Results. Emotional and mental stress before the onset of clinical symptoms was noted in all patients and over 50% of them associate debut of disease with previous stress. Patients with UC significantly more often characterized themselves as nervous people experiencing great stress during daily activity and communication with other persons before the onset of clinical symptoms. These patients felt complete physical and mental exhaustion in the evening compared with healthy respondents. Duration of sleep and bedtime were not the predictors of ulcerative colitis in the population of the Western Siberia. Conclusion. Stress is an essential predictor and possible potential trigger of ulcerative colitis. Duration of sleep and bedtime do not affect the occurrence of ulcerative colitis.