Bedwetting is common for children, affecting more boys than girls. The condition occurs in approximately 15% of children at the age of 5 years, 7% of children at the age of 8, and declines to 1% to 2% of children by the age of 15 years. It continues to affect 0.5% into adulthood. Although children develop bladder control at different rates, most boys can control their bladder during the day and night by the age of 6, and most girls by the age of 5. When a child who is old enough to have bladder control urinates accidentally while sleeping, it's called nocturnal enuresis.

There are two main types of nocturnal enuresis: primary and secondary. The primary type is a condition where a child still wets the bed after age 5 or 6. It's often hereditary. The secondary type occurs when a child who had stopped bedwetting for at least six months starts again, often due to emotional stress or a medical condition.

Possible causes of primary nocturnal enuresis include the following:

• delay in maturation of bladder control or incomplete toilet training
• genetics – children with parents who also wet the bed beyond age 5 are at an increased risk for bedwetting
• sleeping deeply – this may make children less aware of cues for the need to urinate
• Constipation – this may not allow children to empty their bladder completely
• urination patterns – children who suppress their urge to urinate or postpone urinating may not develop coordination with sphincter control and bladder control
• high nighttime urine volume

Rare possible causes include the following:

• problems with antidiuretic hormone (ADH), a hormone that causes the body to retain water – normally, ADH levels increase at night to decrease the amount of urine produced; however, children with enuresis do not have increased ADH levels at night, causing greater urine production, which can lead to bedwetting
• minor nerve damage – this may decrease a child's ability to sense a full bladder

Although it is often said that emotional stress causes primary nocturnal enuresis, there is little scientific evidence to support this claim. However, bedwetting itself may lead to feelings of shame and lowered self-esteem.

Causes of secondary nocturnal enuresis include the following:

• emotional stress (e.g., birth of a sibling, significant loss, family discord)
• urinary tract infection
• Diabetes mellitus (rarely)

For sleeping children who are old enough to control their bladders, the symptoms of bedwetting are obvious. Regularly finding urine-soaked sheets is a clear sign of the problem. Also, a child may wake and cry during the night when the wetting occurs, or wake up caregivers to alert them.

The most common complication of bedwetting is the impact on self-esteem and the emotional distress it causes children. Assuring children that the occurrences are accidental (and not blaming the condition on them) is key to managing the psychological effects. Many children who wet the bed may fear staying overnight at a friend's house in case they wet the bed there.

Since many children under the age of six still wet the bed, any one of the following signs should signal the need to consult a doctor:

• a child over the age of 5 or 6 who still wets the bed
• a child who is wetting during the day after the age of 4 or 5
• a child who starts bedwetting at night after having stopped for six months or more
• urinary symptoms such as urinating frequently or having pain with urination
• excessive weight loss or thirst

Laboratory tests can be done to make sure the bedwetting isn't caused by a urinary tract infection or by other medical conditions such as diabetes. Treatment can be started if these medical conditions are found.