Dear Dr. Greene, My eight 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 is because he has emotional problems. What is the real cause of bed-wetting? Does anybody know? Please don't indicate where this question came from, but please get back to me if you possibly can.

Children who can control their bladders during the day, but who have never 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. Over five million school-age children in the US alone have PNE.

Sadly, most children with PNE feel that there is something wrong with who they are that causes their problem. 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.

In a recent survey of 9,000 parents of kids ages 6 - 17, 22% stated that they thought the reason their child wet the bed was laziness (survey conducted by ICR Survey Group from July 10 1996, through August 6, 1996). I am happy to tell you that this could not be further from the truth! Primary nocturnal enuresis is a common developmental phenomenon related to physical and physiologic factors. It does not 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. Not all children do. 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 individuals make the transition from urinating around-the-clock to only urinating during waking hours. There are three reasons why individuals continue to need to urinate at night:

1. 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.
2. They have bladders that are a little too small to hold the normal amount of urine.
3. They make more urine than their normal-size bladders can hold, for several reasons:
   • They may drink too much. Drinking in the two hours before bed increases nighttime urine production.
   • They may be consuming a diuretic medication, a substance that directly increases urine output. Usually these are not prescribed medications, but caffeinated cola drinks or chocolate.
   • They may make more urine in response to a chronic disease such as diabetes or a chronic urinary tract infection.
   • They may make more urine than average because of their hormonal regulatory systems. Babies make about the same amount of urine around-the-clock. Most adults make less urine while they sleep. The reason for this is thought to be 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 nighttime surge did not happen. Perhaps this is a reason bed wetters tend to make more urine at night.

If an individual consistently has to urinate at night, one or more of the above three reasons is the cause.