Causes and Risk Factors
Primary constipation. Functional (primary) constipation has multiple possible causes.
- In slow transit-constipation, impaired regulation of peristalsis by the enteric nervous system and the muscles of the colon result in delayed passage of stool through the lower digestive tract. Dietary factors such as a low-fiber diet may also contribute.
- Normal-transit constipation is characterized by normal peristalsis and the absence of any pathological findings, but a persistent perception of being constipated and of inadequate evacuation. There is no known cause for this type of constipation beyond its association with psychosocial stress.
- In pelvic floor dysfunction, there is faulty coordination of the muscles that facilitate expulsion of stool from the rectum. Psychological causes have been proposed, and physical trauma plays a role in some cases (Leung, Riutta 2011; Lembo 2003; Rao 2014; Jamshed 2011).
Secondary constipation. Causes of secondary constipation generally fall into five categories:
- Blockages. These include colorectal cancer, bowel stricture (narrowing), abdominal tumor pressing on the colon, and any other cause of bowel obstruction (Basilisco 2013).
- Neurological causes. Conditions that disrupt intestinal neuromuscular signaling can cause secondary constipation (eg, multiple sclerosis, Parkinson’s disease, spinal cord injury, diabetic neuropathy, and stroke) (Basilisco 2013; Rao 2014).
- Hormonal causes. Endocrine conditions, such as hypothyroidism, can cause or contribute to constipation (Basilisco 2013; Rao 2014). Diabetes is associated with constipation; this is thought to be through eventual damage of enteric nerves, altered intestinal muscle contractility and function, and disrupted intestinal microbiota (Yarandi 2014).
- Muscular causes. For some individuals, constipation is caused by difficulty controlling the muscles of the pelvic floor and the external anal sphincter. Injury or trauma to the pelvic muscles can be responsible (Roque 2015; Leung, Riutta 2011).
- Medications. Medications, notably opioid pain relievers, can cause secondary constipation, particularly in the elderly. Other medications less commonly cause secondary constipation: acetaminophen (Tylenol), anticholinergics, antidepressants, antihistamines, antipsychotics, calcium-channel blockers, beta-blockers, diuretics, and non-steroidal anti-inflammatory drugs (Jamshed 2011; Rao 2014; Leung, Riutta 2011).
Female gender. Women are two to three times as likely as men to have chronic constipation (Jamshed 2011; Roque 2015). This may be due to the influence of hormones on digestive function, since many women experience constipation during the luteal phase (last two weeks) of the menstrual cycle (Chu 2014; Oh 2013; Jamshed 2011). Pelvic floor injuries sustained during childbirth may be to blame in another segment of women with chronic constipation (Leung, Riutta 2011; Roque 2015).
Older age. Constipation is more common in older age, with the greatest prevalence among those 70 or older. As many as 70% of institutionalized elderly report daily use of laxatives (Leung, Riutta 2011).