Constipation occurs when bowel movements become difficult or less frequent than normal. Straining during bowel movements, hard stools and two or fewer bowel movements per week are common symptoms. Common causes include lack of fiber in the diet, insufficient water intake, lack of exercise, stress, ignoring the urge to go to the bathroom, overuse of laxatives and disruptions in normal routine. Some medical conditions can also cause constipation, such as hypothyroidism, diabetes, depression, Parkinson's disease, multiple sclerosis, and inflammatory bowel disease. Medications that can cause constipation include calcium channel blockers, diuretics, antidepressants, antihistamines, antacids and painkillers.
Sources: everydayhealth.com, constipation.emedtv.com, medicinenet.com, health.com, webmd.com