Bedwetting: What Causes It?

Waking in the middle of the night to change your child's sheets after a bedwetting episode is practically a rite of passage for parents. And it's more common than you think.

"I call it the hidden problem of childhood," says Howard Bennett, MD, a pediatrician and author of Waking Up Dry: A Guide to Help Children Overcome Bedwetting. "Unlike asthma or allergies, it's just not talked about outside the house."

Bedwetting: The Secret Problem

That secrecy about bedwetting makes the situation tougher for kids and parents alike. "Ninety percent of kids think they're the only ones who wet the bed, which makes them feel even worse," says Bennett.

Yet bed-wetting children are far from alone. Though children naturally gain bladder control at night, they do so at different ages. From 5 to 7 million kids wet the bed some or most nights -- with twice as many boys wetting their bed as girls. After age 5, about 15% of children continue to wet the bed, and by age 10, 95% of children are dry at night.

Wet beds leave bad feelings all around. Frustrated parents sometimes conclude a child is wetting the bed out of laziness. Kids worry there's something wrong with them -- especially when teasing siblings chime in. Fear of wetting the bed at a friend's sleepover can create social awkwardness.

For some, bedwetting may be an inevitable part of growing up, but it doesn't have to be traumatic. Understanding bed-wetting's causes is the first step to dealing with this common childhood problem.

The Bedwetting Gene

There's no one single cause of bed-wetting, but if you want an easy target, look no farther than your own DNA.

"The majority of bedwetting is inherited," says Bennett. "For three out of four kids, either a parent or a first-degree relative also wet the bed in childhood."

Scientists have even located some of the specific genes that lead to delayed nighttime bladder control. (For the record, they're on chromosome 13, 12, and 8.)

"Most parents who had the same problem communicate it to their kids, which is good," suggests Bennett. "It helps a kid understand, I'm not alone, it's not my fault."

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 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.

Bedwetting Treatment: Becoming 'Boss of Your Body'

The potential harm of bedwetting is more often psychological than medical. "After age 6, many children start to have sleepovers, and that's when bed-wetting can be particularly embarrassing and stressful," says Bennett.

"It's just as important to know what doesn't cause bedwetting -- the myths around it," says Bennett. "No child wets the bed on purpose, or from being too lazy to get up to pee."

Dragging themselves out of bed to change wet sheets on yet another night, parents frequently become frustrated. "Intentionally or unintentionally, parents express disapproval that this is happening," says Bennett. "It's understandable, but it makes the situation worse."

Addressing the problem positively can avoid lasting problems, and numerous strategies can help children cope with and improve bedwetting. Some bed-wetting treatments include:

• Encouraging a child to pee before bedtime.
• Restricting a child's fluid intake before bed.
• Covering the mattress with plastic.
• Bed-wetting alarms. These alarms sense urine and wake a child so they can use the toilet.
• Bladder stretching exercises that may increase how much urine the bladder can hold.
• Medications.

Because bedwetting gets better on its own, "in the past, doctors often said to parents and kids, 'Don't worry about it,'" says Bennett. "But if it's causing anxiety or social problems, it's important to know there are things families can do to make the situation better."