Constipation may be a symptom of a medical condition, side effect of a medication or the result of lifestyle choices. In addition, age-related factors, such as decreased activity of the intestinal muscles and enlargement of the rectum, can lead to constipation. Chronic pain and some mental disorders (such as depression) may also cause constipation. The most common causes of constipation are a low-fiber diet and a lack of exercise.

Digestive system disorders that can cause constipation include:

• Irritable bowel syndrome (IBS). Spasms in the colon that affect bowel movements. Contents travel slowly through the intestines in patients with IBS, which can lead to constipation. Patients with IBS often experience alternating episodes of constipation and diarrhea. IBS is one of the most common causes of chronic constipation in the United States.
  
  
• Hemorrhoids/anal fissures. Inflammation and tears around the anus that can cause bleeding, itching and/or pain. Patients with hemorrhoids or anal fissures may withhold stool due to these painful conditions, which may lead to constipation. In addition, hemorrhoids may produce muscle spasms in the anus, which can delay bowel movements, also causing constipation. On the other hand, patients with constipation may develop hemorrhoids or anal fissures by straining during bowel movements and the passage of hard, dry stools through the anus.
  
  
• Compression or obstruction of the intestines. Pressure or tightening of the intestines (strictures) due to scar tissue, tumors, cancer or diverticulitis (inflammation around small pockets called diverticula). This narrowing or blockage can cause constipation.
  
  
• Motility disorders. Restricted ability or inability of intestinal muscles to contract, causing waste to move slowly through the intestines or not at all, which causes constipation. In colonic inertia, food product waste (stool) may remain stored in the middle portion of the colon rather than progressing through it, leading to constipation. Colonic inertia and delayed transit are two types of chronic idiopathic (of unknown origin) constipation that may be related to nerves, hormones or muscles in the colon, rectum or anus. These types of disorders are most common in women.
  
  
• Dyschezia. Poor coordination of pelvic and anal muscles. The inability to relax the pelvic floor muscles (that support the bladder, uterus and rectum) and anal sphincter (that keeps the anus closed) can cause constipation.
  
  
• Colorectal cancer. Uncontrolled growth of abnormal cells in the colon or rectum.

Some medicines may cause constipation. These include:

• Narcotics used to treat pain
• General anesthesia
• Antidepressants
• Antihypertensives (high blood pressure medications)
• Antidiarrheals
• Antacids that contain aluminum or calcium
• Calcium supplements
• Tranquilizers
• Iron supplements
• Antihistamines
• Antispasmodic drugs
• Diuretics (medicine that increases the production of urine)
• Chemotherapy drugs

Although they are sometimes used to treat constipation, laxatives can also cause constipation when used too often. Frequent use of laxatives can interfere with the colon’s natural ability to contract, leading to failure of the intestines to work properly and causing constipation. This is sometimes referred to as lazy bowel syndrome.

Diet or lifestyle issues that can cause constipation include:

• Diet. A low-fiber diet (not enough fresh vegetables, fruits or whole grains) may lead to constipation. Because fiber is not digested by the body, it passes through the intestines virtually unchanged. Its soft texture adds bulk to stool, helping to move waste through the intestines. Soluble fiber (e.g., psyllium, oatmeal) turns to a gel when mixed in fluid. Insoluble fiber (e.g., whole grain breads and cereals) does not dissolve in liquid. Both types aid in relieving constipation. Foods high in fat and sugar (such as many soft, processed foods) can slow the digestive process, causing too much fluid to be absorbed from stool, and leading to constipation.
  
  
• Suppressing the urge to have a bowel movement. Withholding or delaying the release of stool is sometimes done to avoid using public toilets, because it is inconvenient or because a person is busy. It can also occur as the result of severe emotional distress. However, repeatedly resisting the urge to defecate can lead to insensitivity of the intestines. The usual urges are no longer felt and constipation results.
  
  
• Immobility or sedentary lifestyle. Exercise stimulates intestinal activity, helping to regulate bowel movements. A lack of exercise or too much bed rest can lead to constipation.
  
  
• Travel. Changes in a person’s schedule, activity level or diet as the result of traveling may interrupt normal digestive processes and cause constipation.
  
  
• Pregnancy. Hormonal changes that occur during pregnancy may play a role in causing constipation. Later in the pregnancy, added weight of the womb can increase pressure on the intestines, which can cause constipation.
  
  
• Insufficient intake of fluids. Without enough fluids, the body will conserve water in the blood by removing additional water from the stool, leading to hard, dry stool. In addition, drinks containing caffeine (e.g., coffee, cola) or alcohol have a dehydrating effect and can lead to constipation.
  
  
• Habitual use of enemas. Frequent enemas may damage nerve cells in the colon and interfere with the colon’s natural ability to contract. This can lead to a loss of normal functioning and include constipation.
  
  
• Stress. Stress can slow digestion, increasing the amount of water absorbed from waste in the intestines, which can create hard, dry stool difficult to pass.
  
  
• Loss of body salts. When too much salt is absorbed by the kidneys or lost via vomiting or diarrhea. Salt is necessary for the absorption of food in the intestines – too little salt in the body may cause constipation.

Problems outside the digestive tract may also cause constipation by slowing the movement of stool through the large intestine, causing too much fluid to be absorbed. These conditions include:

• Stroke (interruption in the flow of blood to the brain)
  
  
• Spinal cord injuries (damage that affects nerves in the spinal cord)
  
  
• Multiple sclerosis (nerve cell damage affecting the brain and spinal cord)
  
  
• Parkinson’s disease (damage to the area of the brain that controls movement)
  
  
• Diabetes (high levels of sugar in the blood)
  
  
• Underactive thyroid (low levels of metabolism-stabilizing hormones)
  
  
• Scleroderma (connective tissue disease that can harden skin)
  
  
• Lupus (chronic inflammation caused by the body’s own immune system)
  
  
• Eating disorders (may include laxative abuse)