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. Constipation or irregularity, is a condition of the digestive system where a person (or animal) experiences hard feces that are difficult to eliminate; it may be extremely painful, and in severe cases (fecal impaction) lead to symptoms of bowel obstruction. ... Psychology is an academic and applied field involving the scientific study of mental processes and behavior. ... A psychosomatic illness is one with physical manifestations and supposed psychological cause, often diagnosed when any known or identifiable physical cause was excluded by medical examination. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... This article or section does not cite its references or sources. ...

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