Editor-In-Chief: C. Michael Gibson, M.S., M.D.  Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S 
Functional constipation is a form of constipation with a psychological or psychosomatic background. A person suffering from it is physiologically healthy, but still experiences trouble defecating. Functional constipation is medically defined by the Rome III criteria.
Rome III Criteria for Functional Constipation
|Any 2 of the following|
|Less than three evacuations per week|
|Lumpy or hard stools in ≥ 25% of defecations|
|Straining during ≥ 25% of defecations|
|Anorectal obstruction sensation for ≥ 25% of defecations|
|Manual maneuvers to facilitate ≥ 25% of defecations|
|Incomplete evacuation sensation for ≥ 25% of defecations|
|Loose stools are not present|
|Insufficient criteria for irritable bowel syndrome|
† Criteria fulfilled for the past 3 months and symptom onset at least 6 months before diagnosis.
American Gastroenterological Association, however have stopped using the term functional constipation because a subset these patients have slow colonic transit that has been associated with a marked reduction in colonic intrinsic nerves and interstitial cells of Cajal which is against the true definition of functional disorder.
Functional constipation has many causes, some of which are:
- a bad diet
- an unwillingness to defecate
- nervous reactions, including prolonged and/or chronic stress and anxiety, that close the inner anal sphincter muscle, which isn't under voluntary control
- inability or unwillingness to control one's outer anal sphincter, which is normally under voluntary control
- deeper psychosomatic disorders which sometimes affect digestion and the absorption of water in the colon
- ↑ Longstreth GF, Thompson WG, Chey WD, Houghton LA, Mearin F, Spiller RC (2006). "Functional bowel disorders". Gastroenterology. 130 (5): 1480–91. doi:10.1053/j.gastro.2005.11.061. PMID 16678561.
- ↑ Farrugia G (2008). "Interstitial cells of Cajal in health and disease". Neurogastroenterol Motil. 20 Suppl 1: 54–63. doi:10.1111/j.1365-2982.2008.01109.x. PMID 18402642.