What is the real cause of my son's bed-wetting?

By Alan Greene, MD, FAAP
October 03, 2005


My 8-year-old son has wet the bed consistently (about every other night) for as long as I can remember. He feels terrible about it and I feel like a failure as a parent. My mother says it's because he has emotional problems. What is the real cause of bed-wetting? Does anybody know?


Children who can control their bladders during the day, but who haven't been dry at night for at least a six-month period, have what is known medically as primary nocturnal enuresis (PNE), the most common form of bed-wetting. More than five million school-age children in the US alone have PNE.

Sadly, most children with PNE feel that there is something wrong them. Many of them feel that it's the result of either bad thoughts or bad actions. They feel that somehow bed-wetting is a punishment.

Similarly, many parents feel that their children's bed-wetting is a result of a defect in their parenting. This feeling is heightened by well-meaning friends and relatives who bring up questions of emotional instability as the cause of bed-wetting.

Primary nocturnal enuresis is a common developmental phenomenon related to physical and physiologic factors. It doesn't come from emotional stress, poor self-esteem, or emotional immaturity.

Children with PNE have two things in common: First, they need to urinate at night; second, they don't wake up when they need to urinate.

Not all children need to urinate at night. During the first months of life, babies urinate around the clock. Most adults, however, don't need to urinate at night (although a small percentage of the population will need to urinate at night throughout life). Sometime in middle childhood, most children make the transition from urinating around the clock to only urinating during waking hours. Here are some reasons why some people may continue to need to urinate at night:

  • There is an imbalance of the bladder muscles. For example, the muscle that contracts to squeeze the urine out is stronger, at moments, than the sphincter muscle that holds the urine in.
  • They have bladders that are a little too small to hold the normal amount of urine.
  • They make more urine than their normal-size bladders can hold, which may be caused by drinking too much, consuming a diuretic medication, diabetes, or a chronic urinary tract infection.

Another possible cause for making excess urine at night is the hormonal regulatory systems. Babies make about the same amount of urine around the clock. Most adults make less urine while they sleep, due to a nighttime surge of a hormone called antidiuretic hormone (ADH). The levels of ADH found in the blood are higher beginning in the evening. One study looking at ADH levels in bed-wetters, compared to controls, found that there was a constant low level of ADH in the bed-wetters.

The second thing children with PNE have in common is that they don't wake up when they need to urinate. When infants need to urinate, there is no signal that goes from the bladder to the brain to wake them up. On the other hand, when an adult's bladder is full at night, there is a signal that goes from the bladder, through the nervous system, up to the brain. This signaling mechanism comes into play sometime in middle childhood.

For many years, parents of bed-wetting children have claimed that their children were deep sleepers. Physicians have usually disagreed with this, citing evidence from sleep EEGs showing that bed-wetting children went through the same stages of sleep as other children, at the same frequency, and that bed-wetting can occur at any stage of sleep.

So, simply put, children who wet the bed at night need to urinate at night and don't wake up when their bladders are full -- these are the only children who wet the bed.

Understanding the causes of bed-wetting can help remove its stigma. You are also now better equipped to evaluate the suggestions people make to you. Effective therapy is aimed at the underlying causes. Most children can be completely dry within 12 weeks.

The information on this Web site is designed for educational purposes only. It is not intended to be a substitute for informed medical advice or care. You should not use this information to diagnose or treat any health problems or illnesses without consulting your pediatrician or family doctor. Please consult a doctor with any questions or concerns you might have regarding your or your child's condition.

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