Almost all children who wet the bed do not do so intentionally. Most likely, several things are involved when a child older than age 5 continues to wet the bed. Possible causes of primary nocturnal enuresis include:
Delayed development. Children with a less mature nervous system may not be as able to sense when the bladder is full.
Small bladder capacity. Having a smaller-than-normal bladder may make some children more prone to wet the bed.
Too little antidiuretic hormone (ADH). Levels of antidiuretic hormone (ADH), a brain chemical that signals the kidneys to release less water, normally rise at night. Some children who wet their beds may not produce more ADH at night.
Sound sleeping. Many parents note that their child who wets the bed is a deep sleeper. These children usually wet the bed less often as their sleep patterns mature.
Psychological and social factors. Bed-wetting does not appear to be a direct result of emotional problems. In fact, bed-wetting may be the cause of some emotional problems for children. But children living in stressful home situations or in institutions may be more likely to wet the bed.
Some of these things may be inherited. A child is at increased risk for wetting the bed if one or both parents has a history of bed-wetting as a child.