Everyone is affected by constipation now and then — your diet, travel, and a lack of activity can all trigger a brief bout. But you might be surprised by the conditions and other factors that can be responsible for longer term or chronic constipation. The list is wide-ranging, from pregnancy constipation to a side effect of antidepressants.

Some of these causes of constipation can be handled at home with an over-the-counter product or changes in your medicine cabinet, but serious constipation warrants a prompt doctor's visit.

"Constipation that's new, different, associated with bleeding or weight loss, and lasts a couple of days may be a sign of colon cancer," says gastroenterologist Benjamin Krevsky, MD, associate chief of the section of gastroenterology at Temple University in Philadelphia, Pa. But since there are several more common causes of constipation that aren't as serious, don't worry too much. Your doctor can help you determine what's really behind your constipation.