Ulcerative colitis (UC) is a subset disorder of inflammatory bowel disease (IBD) with chronic course and symptoms such as fatigue, gastrointestinal pain, fever, etc. IBD is associated with psychological manifestations including depression and anxiety. There is an increased number of studies trying to link these comorbidities. The gut-brain axis is regulated by intestinal microbiota and this bidirectional communication including immune, neural, endocrine and metabolic mechanisms may bring us closer to the answer. The following case concerns a 56-year-old patient with history of major depressive disorder who was in continuous psychiatric care and treated with antidepressants. Several years after the beginning of psychiatric treatment, he was hospitalized for diagnostic examination due to subfebrility of unknown etiology, but with no final somatic diagnosis. After two years he was referred to our department and at administration the patient showed symptoms of depression, anxiety, lack of motivation and suicidal thoughts and tendencies. Subfebrility was still present at that time. His psychopharmacotherapy was revised and there was a slight improvement in mood and behaviour. During outpatient follow-ups the symptoms of depression were still prominent and remission was not achieved even with modulation of antidepressant pharmacotherapy. The following year the patient was diagnosed with UC and started specific treatment after he presented with diarrhea in addition to subfebrility. Subsequently his mood improved, suicidal thoughts were diminished and ultimately remission was achieved. This case suggests that only after UC was being treated the psychiatric symptoms also withdrew which implicates that inflammatory mediators were involved in pathogenesis of depression.