Bedwetting (or sleepwetting) is involuntary urination while asleep after the age at which bladder control would normally be anticipated. Doctors call this condition, "Nocturnal Enuresis."
Primary Nocturnal Enuresis (PNE) is when a child has not yet stayed dry on a regular basis
Secondary Nocturnal Enuresis is when a child or adult begins wetting again after having stayed dry
Parents tend to consider bedwetting a problem earlier than do physicians. Most children (85-90%) will consistently stay dry by age 6. By age 10, 95% of children are dry at night. Studies place adult bedwetting rates at between 0.5% to 2.3%.
A small percentage (5% to 10%) of bedwetting cases are caused by specific medical situations. Most cases, however, do not have a specific identifiable cause. 
Treatment ranges from behavioral-based options to medication. Much of the rationale for treatment revolves around protecting/improving the patient’s self-esteem (Ilyas & Jerkins, 1996). .
Most bedwetting can be described as, "a bothersome alteration in normal development."  The usual development process is:
Infants: Void by reflex
One- and two-year olds: Bladder grows larger and the brain develops the ability to sense bladder fullness (McLorie & Husmann, 1987)
Two- and three-year olds: Develop the ability to void or inhibit voiding
Four- and five-year-olds: Develop an adult pattern of urinary control
Frequency of bedwetting (epidemiology)
Males are more likely to wet the bed than females. Males make up 60% of bed-wetters overall and make up more than 90% of those who wet nightly (Schmitt, 1997).
Doctors frequently consider bedwetting as a self-limiting problem, since most children will grow out of it.
Approximate bedwetting rates are:
Age 5: 20%
Age 6: 10 to 15%
Age 7: 7%
Age 10: 5%
Age 15: 1-2%
Age 18-64: 0.5%-1% 
Children 5 to 9 years old have a spontaneous cure rate of 14% per year. Adolescents 10 to 18 years old have a spontaneous cure rate of 16% per year.
As can be seen from the numbers above, 5% to 10% of bedwetting children will not outgrow the problem, leaving 0.5% to 1% of adults still dealing with bedwetting.  Individuals who are still enuretic at age 18 are likely to deal with bedwetting throughout their lives. Adult rates of bedwetting show little change due to spontaneous cure.
Studies of bedwetting in adults have found varying rates. The most-quoted study in this area was done in the Netherlands. It found a 0.5% rate for 18-64 year olds. A Hong Kong study, however, found a much higher rate. The Hong Kong researchers found a bedwetting rate of 2.3% in 16 to 40 year olds. 
Medical definitions (clinical criteria): primary vs. secondary enuresis
The medical name for bedwetting is nocturnal enuresis. The condition is divided into two types: primary nocturnal enuresis (PNE) and secondary nocturnal enuresis.
Primary nocturnal enuresis (PNE)
Primary nocturnal enuresis occurs when a child is beyond the age at which bladder control would normally be anticipated and:
Continues to average at least two wet nights a week with no long periods of dryness, or
Would not sleep dry without being taken to the toilet by another person
Some medical definitions list primary nocturnal enuresis (PNE) as a clinical condition at between 4-5 years old. This type of classification is frequently used by insurance companies. It defines PNE as, “persistent bedwetting in the absence of any urologic, medical or neurological anomaly in a child beyond the age when over 75% of children are normally dry.” 
Other definitions for PNE cast themselves as more “practical” guidance, saying that bedwetting can be considered a "clinical problem" if the child is unable to keep the bed dry by age seven. 
D'Alessandro refines this to bedwetting more than 2x/month after the age:
6 years for females
7 years for males. 
Secondary nocturnal enuresis
Secondary enuresis occurs after a patient goes through an extended period of dryness at night (approx. 6 months or more) and then reverts to night-time wetting. Secondary enuresis can be caused by emotional stress or a medical condition, such as a bladder infection. 
U.S. psychological definition
Psychologists may use a definition from the American Psychiatric Association’s DSM-IV, defining nocturnal enuresis as repeated urination into bed or clothes, occurring twice per week for at least 3 consecutive months in a child of at least 5 years of age and not due to either a drug side effect or a medical condition. Even if the case does not meet this criteria, the DSM-IV definition allows psychologists to diagnose nocturnal enuresis if the wetting causes the patient clinically significant distress. 
When treatment is recommended
Doctors consider medical evaluation/intervention when:
The physician suspects a bladder abnormality
Lab tests show an infection or other medical condition like diabetes
The bedwetting is harming the child’s self-esteem or relationships with family/friends
Only a small percentage of bedwetting is caused by the first two items (see below). Most treatment is covered under the third, with physicians being concerned about the child's emotional welfare.
Parents become concerned much earlier than doctors. A study in 1980 asked parents and physicians the age that children should stay dry at night. The average responses were:
Parents: 2.75 years old
Physicians: 5.13 years old. 
Normal processes of staying dry (regulation in the organism)
Children usually achieve nighttime dryness by developing one or both of two abilities. There appear to be some hereditary factors in how and when these develop.
One is a hormone cycle in which a minute burst of antidiuretic hormone happens daily at about sunset reducing kidney output of urine well into the night so the bladder doesn't get full until morning. This hormone cycle is not present at birth. Many children develop it between the ages of two and six years old, others between six and the end of puberty, and some not at all.
The other is the ability to awaken before wetting. The body normally develops the ability to wake when the bladder is full.
Causes of and increased risks for bedwetting
The following list summarizes bedwetting's known causes and risk factors. Enuretic patients frequently have more than one cause or risk factors from the items listed below.
Most cases of bedwetting are PNE-type, which has two related most-common causes:
Neurological-developmental delay This is the most common cause of bedwetting. Most bedwetting children are simply delayed in developing the ability to stay dry and have no other developmental issues. 
Genetics Bedwetting has a strong genetic component. Children whose parents were not enuretic have only a 15% incidence of bedwetting. When one or both parents were bedwetters, the rates jump to 44% and 77% respectively.  Genetic research shows that bedwetting is associated with the genes 13q and 12q (possibly 5 and 22 also). 
There is no test to prove that bedwetting is only a developmental delay and genetic testing offers little or no benefit to a bedwetting patient.
Other proven causes
Doctors examining a bedwetting patient will search for the following, less frequent, causes of nocturnal enuresis. These causes are more common in secondary nocturnal enuresiscases. Only a small percentage of primary-nocturnal-enuresis type bedwetting is caused by one of the following specifically-identifiable causes. 
Infection/disease Infections and disease are more strongly connected with secondary nocturnal enuresis and with daytime wetting. Less than 5% of all bedwetting cases are caused by infection or disease, the most common of which is a urinary tract infection. 
Physical abnormalities Less than 10% of enuretics have urinary tract abnormalities, such as a smaller than normal [bladder]. Current data does support increased bladder tone in some enuretics, which functionally would decrease bladder capacity. 
Insufficient anti-diuretic hormone (ADH) production A portion of bedwetting children do not produce enough of the [Anti-Diuretic Hormone]. Normally ADH increases at night. This increase doesn't occur in child enuretics, but does occur in adolescent enuretics. The diurnal change may not be seen until ~age 10. 
Psychological Psychological issues (e.g., death in the family, sexual abuse, extreme bullying) are established as a cause of secondary nocturnal enuresis (a return to bedwetting), but are very rarely a cause of PNE-type bedwetting.   When Enuresis is caused by a psychological disorder, the bedwetting is considered a symptom of the disorder. Enuresis does have a psychological diagnosis code (see previous section), but it is not considered a psychological condition itself. (See section on psychological/social impact, below)
More severe neurological-developmental issues Patients with mental handicaps, such as Down syndrome, have a higher rate of bedwetting problems. One study of seven year olds showed that, "handicapped and mentally retarded children," had a bedwetting rate almost three times higher than non-handicapped children (26.6% vs. 9.5%, respectively).
Heavy sleeping Many parents report that their bedwetting children are heavy sleepers. Research in this has some contradictory results. Studies show that children wet the bed during allphases of sleep, not just the deepest (stage four). A recent study, however, showed that enuretic children were harder to wake.  Some literature does show a possible connection between sleep disorders and ADH production. Insufficient ADH might make it more difficult to transition from light sleep to being awake. 
Stress Stress is controversial as a possible cause of primary nocturnal enuresis (PNE), but is well established as a cause of a child who returns to bedwetting (secondary nocturnal enuresis). Some sources report that, “Psychologists and other mental health professionals regularly report that children begin wetting the bed during times of conflict at home or school. Dramatic changes in home and family life also appear to lead some children to wet the bed. Moving to a new town, parent conflict or divorce, arrival of a new baby, or loss of a loved one or pet can cause insecurity that contributes to bedwetting.”  Other sources contradict this, saying, “Doctors have found no relationship to social background, life stresses, family constellation, or number of residencies.” . However, the stress on many children caused by government ordered wartime evacuation has led to several studies showing that there was a direct effect on children . Indeed, in Britain at the beginning of WWII, enuresis was known as the "evacuee's disease".
Food allergies For some patients, food allergies may be part of the cause. This link is not well established, requiring further research. 
Improper toilet training This is another disputed cause of bedwetting. This theory was more widely supported in the last century and is still cited by some authors today. Some say bedwetting can be caused by toilet training that is started too early or is too forceful. Recent research has shown more mixed results and a connection to toilet training has not been proved or disproved.
Dandelions Anecdotal reports and folk wisdom says children who handle dandelions can end up wetting the bed. Dandelions are reputed to be a potent diuretic. English folk names for the plant are "peebeds" and "pissabeds". In French dandelions are called pissenlit, which means "urinate in bed"; likewise "piscialletto", an Italian folkname, and "meacamas" in Spanish.
A review of medical literature shows doctors consistently stressing that a bedwetting child is not at fault for the situation. Many medical studies state that the psychological impacts of bedwetting are more important than the physical considerations. “It is often the child's and family member's reaction to bedwetting that determines whether it is a problem or not.” 
Impact on self-esteem
Bedwetting children feel effects ranging from feeling cold on waking, being teased by siblings, being punished by parents, and being afraid that friends will find out.
Whether bedwetting causes low self-esteem remains a subject of debate, but several studies have found that self-esteem improved with management of the condition.  
Children questioned in one study ranked bedwetting as the third most stressful life event, after parental divorce and parental fighting. Adolescents in the same study ranked bedwetting as tied for second with parental fighting. 
Psychologists report that the amount of psychological harm depends on whether the bedwetting harms self-esteem or development of social skills. Key factors are:
How much the bedwetting limits social activities like sleep-overs and campouts 
The degree of the social ostracism by peers 
Anger, punishment, and rejection by caregivers 
The number of failed treatment attempts 
The longer the child has been wetting/older the child is 
Studies show that bedwetting children are more likely to have behavioral problems.
For children who have developmental problems, the behavioral problems and the bedwetting are frequently part of/caused by the developmental issues.
For bedwetting children without other developmental issues, these behavioral issues can result from self-esteem issues and stress caused by the wetting. 
As mentioned previously, current studies show that is is very rare for a child to intentionally wet the bed as a method of acting out.
Historical psychological perspective on bedwetting
Psychological theory through the 1960s placed much greater focus on the possibility that a bedwetting child might be acting out, purposefully striking back against parents by soiling linens and bedding. (More recent research and medical literature states that this is very rare.)
Punishment for bedwetting: rates and effects
Medical literature states and studies show that punishing or shaming a child for bedwetting will frequently make the situation worse. Doctors describe a downward cycle where a child punished for bedwetting feels shame and a loss of self-confidence. This can cause increased bedwetting incidents, leading to more punishment/shaming, “an escalating cycle of wetting accidents and shame.” 
In the United States, about 25% of enuretic children are punished for wetting the bed.  In Hong Kong, 57% of enuretic children are punished for wetting. 
Parents with only a grade-school level education punish bed-wetting children at twice the rate of high school- and college-educated parents. 
Impact on families
Parents and family members are frequently stressed by a child’s bedwetting. Soiled linens and clothing cause additional laundry. Wetting episodes can cause lost sleep if the child wakes and/or cries, waking the parents. A European study estimated that a family with a child who wets nightly will pay about $1,000 a year for additional laundry, extra sheets, disposable absorbent garments such as diapers, and mattress replacement. 
Despite these stressful effects, doctors emphasize that parents should react patiently and supportively. 
Treatment and management options
There are a number of treatment and condition-management options for bedwetting. The following options apply when the bedwetting is not caused by a specifically-identifiable medical condition such as a bladder abnomality or diabeties.
It is important to note that punishment is not effective and can interfer with treatment.
Treatment options with high success rates
Waiting Almost all children will outgrow bedwetting. For this reason, urologists and pediatricians frequently recommend delaying treatment until the child is at least six or seven years old. Physicians may begin treatment earlier if they perceive the condition is damaging the child’s self-esteem and/or relationships with family/friends.
Bedwetting alarms Physicians also frequently suggest bedwetting alarms which sound a loud tone when they sense moisture. This can help condition the child to wake at the sensation of a full bladder. These alarms are considered effective, with study participants being 13 times more likely to become dry at night. There is a 29% to 69% relapse rate, however, so the treatment may need to be repeated. 
DDAVP (Desmopressin) Desmopressin tablets are a synthetic replacement for antidiuretic hormone, the hormone that reduces urine production during sleep. Desmopressin is usually used in the form of Desmopressin acetate, DDAVP. Patients taking DDAVP are 4.5 times more likely to stay dry than those taking a placebo.  The drug replaces the hormone for that night with no cumulative effect. US drug regulators have banned using Desmopressin nasal sprays for treating bedwetting, but say that Desmopressin pills are still considered a safe bedwetting treatment for otherwise healthy patients. The regulators reviewed the drug after two children using Desmopressin nasal sprays died from Hyponatremia, an imbalance of sodium levels in the body. 
Tricyclic antidepressants Tricyclic antidepressantprescription drugs with anti-muscarinic properties have been proven successful in treating bedwetting, but also have an increased risk of side effects. These drugs include Amitriptyline, Imipramine and Nortriptyline). Studies find that patients using these drugs are 4.2 times as likely to stay dry as those taking a placebo. The relapse rates after stopping the medicines are very high--close to 50%.
Condition management options
Diapers Diapers can reduce the embarrassment and mess of wetting incidents. Diaper sizes for enuresis cover individuals from 38 lb (17 kg) through adult sizes. Some research, however, indicates that extended use of diapers can interfere with learning to stay dry. 
Unproven/ineffective treatment options
Dry bed training Dry bed training consists of a strict schedule of waking the child at night, attempting to condition the child into waking by himself/herself.  Studies show this training is ineffective by itself  and does not increase the success rate when used in conjunction with a bedwetting alarm. 
Star chart A star chart allows a child and parents to track dry nights, either as a record and as part of an reward program. This can be done either alone or with other treatments. There is no research to show effectiveness, either in reducing bedwetting or in helping self-esteem.  Some pychologists, however, recommend star charts as a way to celebrate successes and help a child's self-esteem.