Nighttime diarrhea can cause anxiety and discomfort. Diarrhea is a condition when you pass loose, watery stools. Nighttime diarrhea occurs at night and often disrupts your sleep. There are many causes that can lead to diarrhea at night. You may only have mild diarrhea, which will resolve within one or two days. Or, you may experience chronic nighttime diarrhea. Chronic diarrhea lasts for more than four weeks and may indicate a more serious health condition. You should consult a doctor if the diarrhea is severe or chronic.