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Children's Health

Bedwetting: What Causes It?

It's a myth that laziness causes bedwetting. Millions of kids wet the bed -- but why? And how can you help
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The Usual Bedwetting Suspects

Yet genetics only tells part of the story. Researchers have identified a number of factors that likely contribute to bedwetting. "All of these are debated, but each probably plays a role in some children," says Bennett, including:

  • Delayed bladder maturation. "Simply put, the brain and bladder gradually learn to communicate with each other during sleep, and this takes longer to happen in some kids," Bennett tells WebMD.
  • Low anti-diuretic hormone (ADH). This hormone tells the kidneys to make less urine. Studies show that some kids who wet the bed release less of this hormone while asleep. More urine can mean more bedwetting.
  • Deep sleepers. "Families have been telling us for years that their children who wet the bed sleep more deeply than their kids that don't," says Bennett. Research confirms the link. "Some of these children sleep so deeply, their brain doesn't get the signal that their bladder is full."
  • Smaller "functional" bladder. Although a child's true bladder size may be normal, "during sleep, it sends the signal earlier that it's full," says Bennett. 
  • Constipation. Full bowels press on the bladder, and can cause uncontrolled bladder contractions, during waking or sleep. "This is the one that's hiding in the background," says Bennett. "Once kids are toilet trained, parents often don't know how often a child is going ... [they're] out of the 'poop loop.'"

Bedwetting: When Is It Worth Worrying?

Bedwetting that's caused by medical problems is genuinely rare -- 3% of cases or less, according to Bennett. Urinary tract infections, sleep apnea, diabetes, spinal cord problems, and deformities of the bladder or urinary tract -- all are worth mentioning, but probably not worrying over.

Medical causes of bedwetting are nearly always uncovered by simply talking to a child and her parents, performing an exam, and testing the urine, says Bennett.

"The vast majority of kids who are wet at night have nothing medically wrong with them," he emphasizes.

Children who have gained nighttime bladder control, then "relapsed" into bedwetting, are slightly more likely to have medical causes. Psychological stress (such as divorce or the birth of a new sibling) is an even more common cause, though.

Pediatricians don't diagnose primary nocturnal enuresis (the medical term for bedwetting) until age 6. It's an arbitrary cutoff -- after all, 12% of children wet the bed at that age. "It's really only a problem when either the child or the parents start to think so," says Bennett.

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