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The 6 key causes of bedwetting

So, what really causes bedwetting?




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The causes are not simple and differ between children. It is certainly true to say that the most likely cause is a combination of causes. Below is a list of possible causes, all of which have a basis in scientific evidence.

  • The child makes too much urine at night
  • They have small bladders
  • They have an inability to wake up from deep sleep
  • They have bladder dysfunction
  • They have a brain/bladder communication issue
  • There is a hereditary element to bed wetting

You do not need to know what the specific cause of your child’s bedwetting is to get rid of it.

The child makes too much urine at night.

As we grow older, usually at about 3-4 years our body starts to produce a hormone that stops us from producing so much urine at night. The hormone is called Anti-diuretic hormone (ADH) also referred to as arginine vasopressin (AVP). It means that we produce about half our day-time amount at night. Some bed-wetters do not produce enough of this hormone6 meaning that they continue to produce the same amount of urine in the day as at night. At the very least, this means that they would be getting up to empty their bladders if indeed they woke up to do so. It may be that they take longer in their development to start producing this hormone than others.

Their bladders are small

Some studies have shown that bedwetting children have bladders with less than half the capacity of children who are dry9. Why would this be? One explanation is that if your bladder is emptying at random during the night, it never gets a chance to grow. Your brain doesn’t get the message to hold on to the urine and so the bladder empties and stays small. Restricting fluids would also keep the bladder small, as would not drinking enough fluids in the day and lifting at night.

They have a sleep disorder which is an inability to wake up from deep sleep.

This is the research that I found most interesting. When I spoke to other mothers and doctors about bedwetting, the majority of them told me that their child is a “very deep sleeper”. It seems to be very common amongst bedwetting children.

In fact, all the most recent research shows that bedwetting children have the same pattern of sleep (in that it shows the same variance and individuality) as non-bedwetting children and that the sleep disorder is actually about how difficult they are to wake up. Parents like us think that our child is sleeping deeply, when in fact they are just difficult to wake up.

So they sleep deeply, in the sense that they are difficult to arouse from sleep, but not in the sense that they sleep any differently from other children6,7,12. In fact, some studies show that they have marginally lighter sleep than non bedwetting children but are still more difficult to arouse.

Some theories suggest that it is this sleep arousal disorder that we inherit. Other symptoms of this sleep arousal disorder are night terrors and sleep walking7.

So if relatives have this sleep pattern (as demonstrated by sleep walking or night terrors) and the child has some of these other causes too they are more likely to wet the bed.

They have a bladder dysfunction

Some studies have found that the muscle at the mouth of the bladder which is responsible for pushing the urine out of the bladder (the detrusor muscle) is hyperactive at night6,9. This means that the bladder is active all night and the brain is getting signals all night which it doesn’t respond to, leading to disturbed sleep. It seems that the body over compensates for this constant disturbance and becomes difficult to arouse.

I’m sure you are beginning to see how these causes are interlinked.

There is a delay in the brain/bladder connection

Over time, children develop a connection between their bladder being full and the need for the pelvic floor to stay shut so that they don’t wet themselves at night.

It seems that some children are slower to make this connection and the brain does not get the message to keep the urine in the bladder. Some children are dry at night from as early as two years old and so have developed this connection early.

Our central nervous system is responsible for all the brain/body connections and it is thought that some children have a developmental delay in some parts of it.

Also, if your bladder is overactive and/or you have a sleep arousal problem, your brain won’t get the message either. This cause is also a “which came first the chicken or the egg” category of cause.

It is hereditary

Several genes have now been isolated for bedwetting and we know that you have a greatly increased chance of wetting the bed if there is a family history of it10.

It is not clear what exactly is inherited. Is it the sleep arousal problem, the bladder dysfunction, the lack of ADH or the lack of brain/bladder connection?

Of course we can’t do much about the fact that it can be inherited but it is interesting to know. If one waits until the child grows out of bed wetting, it seems that they stop wetting at a similar age to their relation.

How do I know what the cause is for my child?

Simply, unless we subject our child to scientific experimentation, we are unlikely to know which combination is affecting our specific child. Frankly, scientists do not have definitive answers yet and you do not need to know the exact cause for your child for the treatment to be successful.

This is why it is essential to address as many of the causes as possible when we decide that it is time for our child to be dry.

Again, if you are worried about an underlying medical problem or your child has serious day-time wetting, constipation or bowel issues, it is best to go to your doctor.



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