title: Observational research:  the pitfall of drawing firm conclusions about efficacy.
authors.forename: A H
authors.initials: AH
authors.lastname: Daling
authors.forename: Gea A
authors.initials: GA
authors.lastname: Holtman
authors.forename: Margriet M
authors.initials: MM
authors.lastname: Laseur
authors.forename: M A E
authors.initials: MA
authors.lastname: Weinans
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Lisman-van Leeuwen
mesh_terms: D000639:Amitriptyline / Q000627:therapeutic use*; D000929:Antidepressive Agents, Tricyclic / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007099:Imipramine / Q000627:therapeutic use*; D043183:Irritable Bowel Syndrome / Q000188:drug therapy*; D008297:Male
chemical_list: D000929:Antidepressive Agents, Tricyclic; D000639:Amitriptyline; D007099:Imipramine