Certain inherited genes appear to contribute to incontinence. In 1995, Danish researchers announced they had found a site on human chromosome 13 that is responsible, at least in part, for nighttime wetting. If both parents were enuretic, 77% of their children are too; if only one parent was enuretic, then 44% of their offspring are also. Experts believe that other, undetermined genes also may be involved in incontinence.

Experts suggest that anxiety-causing events occurring in the lives of children ages 2 to 4 might lead to incontinence before the child achieves total bladder control. Anxiety experienced after age 4 might lead to wetting after the child has been dry for a period of 6 months or more. Such events include angry parents, unfamiliar social situations, and overwhelming family events such as the birth of a brother or sister.

Incontinence itself is an anxiety-causing event. Strong bladder contractions leading to leakage in the daytime can cause embarrassment and anxiety that lead to wetting at night.

Daytime wetting is more common in girls than in boys, but bedwetting is three times as prevalent in boys (i.e., around 75% of sufferers are male). At the age of 7 approximately 3% of girls and 2% of boys experience functional daytime wetting at least once a week.

Common causes include, but not limited to:

- Incomplete emptying of the bladder

- Irritable bladder

- Constipation

- Stress

- Urinary tract infection

- Urgency (not “making it” to the bathroom in time)

- Anatomic abnormality

- Poor toileting habits

- Small bladder capacity

- Medical conditions like overactive bladder disorder

Most girls can stay dry at night by age six and most boys stay dry by age seven. Boys are three times more likely to wet the bed than girls.

Doctors frequently consider bedwetting as a self-limiting problem, since most children will outgrow it. 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.

Approximate bedwetting rates are:

- Age 5: 20%

- Age 6: 10–15%

- Age 7: 7%

- Age 10: 5%

- Age 15: 1–2%

- Age 18–64: 0.5–1%

As can be seen from the numbers above, a portion of bedwetting children will not outgrow the problem. Adult rates of bedwetting show little change due to spontaneous cure. Persons who are still enuretic at age 18 are likely to deal with bedwetting throughout their lives.

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- to 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.

Favorable response to treatment with the ADHD drug methylphenidate (Ritalin) has been reported, but this treatment option is not acceptable to all patient families.

Dr. Lane Robson, of The Children’s Clinic in Calgary, Alberta, says "If a child is having a wetting episode once a month, medicating them daily is probably not a good treatment. If it’s a daily issue, you may have to make that decision."

The aetiology of NE is not fully understood, although there are three common causes: excessive urine volume, poor sleep arousal, and bladder contractions. Differentiation of cause is mainly based on patient history and fluid charts completed by the parent or carer to inform management options.

The following list summarizes bedwetting's known causes and risk factors. Enuretic patients frequently have more than one cause or risk factor 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. Studies suggest that bedwetting may be due to a nervous system that is slow to process the feeling of a full bladder.

- 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 on chromosomes 13q and 12q (possibly 5 and 22 also).

These first two items are the most common factors in bedwetting, but current medical technology offers no easy testing for either cause. There is no test to prove that bedwetting is only a developmental delay, and genetic testing offers little or no benefit.

As a result, other conditions should be ruled out. The following causes are less common, but are easier to prove and more clearly treated:

- Alcohol consumption Drinking alcohol increases urine production, inhibits anti-diuretic hormone production, decreases awareness, increases drowsiness and causes impulsive decisions.

- Anti-diuretic hormone (ADH) Anti-diuretic hormone regulates urine production by increasing water reabsorption in the kidney. Both insufficient production of ADH, or insufficient response to ADH, leads to an overproduction of urine, often beyond the capacity of a child's bladder. The body normally increases ADH levels at night, signalling the kidneys to produce less urine. The diurnal change may not be seen until about age 10. In some bed wetting children this increase in ADH production does not occur, while other children may produce an increased amount of ADH but their response is insufficient.

- Attention deficit hyperactivity disorder (ADHD) Children with ADHD are 2.7 times more likely to have bedwetting issues.

- Caffeine Caffeine increases urine production.

- Constipation Chronic constipation can cause bed wetting. When the bowels are full, it can put pressure on the bladder. Often such children defecate normally, yet they retain a significant mass of material in the bowel which causes bed wetting.

- Infection/disease Infections and disease are more strongly connected with 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.

- More severe neurological-developmental issues Patients with intellectual disabilities have a higher rate of bedwetting problems. One study of seven-year-olds showed that "handicapped and intellectually disabled children" had a bedwetting rate almost three times higher than "non-handicapped children" (26.6% vs. 9.5%, respectively).

- 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.

- Psychological Psychological issues (e.g., death in the family, sexual abuse, extreme bullying) are established as a cause of (a return to bedwetting), but are very rarely a cause of PNE-type bedwetting. Bedwetting can also be a symptom of a pediatric neuropsychological disorder called PANDAS. When enuresis is caused by a psychological or neuropsychological disorder, the bedwetting is considered a "symptom" of the disorder. Enuresis has a psychological diagnosis code (see previous section), but it is not considered a psychological condition itself. (See section on psychological/social impact, below)

- Sleep apnea Sleep apnea stemming from an upper airway obstruction has been associated with bedwetting. Snoring and enlarged tonsils or adenoids are a sign of potential sleep apnea problems.

- Sleepwalking Sleepwalking can lead to bedwetting. During sleepwalking, the sleepwalker may think he/she is in another room. When the sleepwalker urinates during a sleepwalking episode, he/she usually thinks they are in the bathroom, and therefore urinate where they think the toilet should be. Cases of this have included opening a closet and urinating in it; urinating on the sofa and simply urinating in the middle of the room.

- Stress Stress is not a cause of "primary" nocturnal enuresis (PNE), but is well established as a cause of returning to bedwetting (). Researchers studying children who have yet to stay dry find "no relationship to social background, life stresses, family constellation, or number of residencies." On the other hand, stress is a cause of people who return to wetting the bed. Researchers find that 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, contributing to returning bedwetting.

- Type 1 Diabetes Mellitus Nocturnal enuresis could be the presenting symptom of type 1 diabetes mellitus, classically associated with polyuria, polydipsia, and polyphagia; weight loss, lethargy, and diaper candidiasis may also be present in those with new-onset disease.

Episodes of giggle incontinence are embarrassing and socially incapacitating, diminishing the quality of life. Those having the condition learn to adapt by avoiding activities that may bring on laughter. Other approaches include limiting fluid intake, trying to remain seated, and concealing leakage by wearing absorbent pads and dark clothing.

Globally, up to 35% of the population over the age of 60 years is estimated to be incontinent.

In 2014, urinary leakage affected between 30% and 40% of people over 65 years of age living in their own homes or apartments in the U.S. Twenty-four percent of older adults in the U.S. have moderate or severe urinary incontinence that should be treated medically.

Bladder control problems have been found to be associated with higher incidence of many other health problems such as obesity and diabetes. Difficulty with bladder control results in higher rates of depression and limited activity levels.

Incontinence is expensive both to individuals in the form of bladder control products and to the health care system and nursing home industry. Injury related to incontinence is a leading cause of admission to assisted living and nursing care facilities. More than 50% of nursing facility admissions are related to incontinence.

Men tend to experience incontinence less often than women, and the structure of the male urinary tract accounts for this difference. It is common with prostate cancer treatments. Both women and men can become incontinent from neurologic injury, congenital defects, strokes, multiple sclerosis, and physical problems associated with aging.

While urinary incontinence affects older men more often than younger men, the onset of incontinence can happen at any age. Estimates in the mid-2000s suggested that 17 percent of men over age 60, an estimated 600,000 men, experienced urinary incontinence, with this percentage increasing with age.

There are a number of factors that could potentially contribute to the development of feeding and eating disorders of infancy or early childhood. These factors include:

- Physiological – a chemical imbalance effecting the child's appetite could cause a feeding or eating disorder.

- Developmental – developmental abnormalities in oral-sensory, oral-motor, and swallowing can impact the child's eating ability and elicit a feeding or eating disorder.

- Environmental – simple issues such as inconsistent meal times can cause a feeding or eating disorder. Giving the child food that they are not developmentally acquired for can also cause these disorders. Family dysfunction and sociocultural issues could also play a role in feeding or eating disorders.

- Relational – when the child is not securely attached to the mother, it can cause feeding interactions to become disturbed or unnatural. Other factors, such as parental emotional unavailability and parental eating disorders, can cause feeding and eating disorders in their children.

- Psychological and behavioral – these factors include one involving the child's temperament. Characteristics such as being anxious, impulsive, distracted, or strong-willed personality types are ones that could affect the child's eating and cause a disorder. The individual could have learned to reject food due to a traumatic experience such as choking or being force fed.

Obstructive sleep apnea (OSA) affects around 4% of men and 2% of women in the United States. In general, this disorder is more prevalent among men. However, this difference tends to diminish with age. Women experience the highest risk for OSA during pregnancy. Also, they tend to report experiencing depression and insomnia in conjunction with obstructive sleep apnea. In a meta-analysis of the various Asian countries, India and China present the highest prevalence of the disorder. Specifically, about 13.7% of the Indian population and 7% of Hong-Kong's population is estimated to have OSA. The two groups experience daytime OSA symptoms such as difficulties concentrating, mood swings, or high blood pressure, at similar rates (prevalence of 3.5% and 3.57%, respectively).

Physical and emotional changes are often the most indicative symptoms of feeding and eating disorders of infancy or early childhood. The child's growth and development may be delayed due to the lack of necessary nutrients. The child will usually weigh much less than other children. Withdrawal and irritability are often associated with children that are malnourished.

A systematic review states 7.6% of the general population experiences sleep paralysis at least once in their lifetime. Its prevalence among men is 15.9% while 18.9% of women experience it. When considering specific populations, 28.3% of students and 31.9% of psychiatric patients have experienced this phenomenon at least once in their lifetime. Of those psychiatric patients, 34.6% have panic disorder. Sleep paralysis in students is slightly more prevalent for those of Asian descent (39.9%) than other ethnicities (Hispanic: 34.5%, African descent: 31.4%, Caucasian 30.8%).

Psychogenic polydipsia is found in patients with mental illnesses, most commonly schizophrenia, but also anxiety disorders and rarely affective disorders, anorexia nervosa and personality disorders. PPD occurs in between 6% and 20% of psychiatric inpatients. It may also be found in people with developmental disorders, such as those with autism. While psychogenic polydipsia is usually not seen outside the population of those with serious mental disorders, it may occasionally be found among others in the absence of psychosis, although there is no existent research to document this other than anecdotal observations. Such persons typically prefer to possess bottled water that is ice-cold, consume water and other fluids at excessive levels. However, a preference for ice-cold water is also seen in diabetes insipidus.

Although primary polydipsia is usually categorised as psychogenic, there are some rare non-psychogenic causes. An example is polydipsia found in patients with autoimmune chronic hepatitis with severely elevated globulin levels. Evidence for the thirst being non-psychogenic is gained from the fact that it disappears after treatment of the underlying disease.

A variety of inciting infections have been observed. The most common infection sites are in the upper respiratory tract: including rhinitis, sinusitis, and pharyngitis. The specific microbe most commonly recognized has been group A Streptococcus. Mycoplasma pneumonia, influenza, and other common viruses have also been noted. Influenza has often been well-documented anecdotally at both initial onset and exacerbations of PANS.

A number of additional infections, including gastrointestinal infections, dental infection, herpes simplex, varicella, Epstein-Barr virus, enterovirus, Kawasaki disease, and anaphylactoid purpura, have been mentioned to be associated with the onset or exacerbation of PANS symptoms in a small number of cases.

At the time of first PANS presentation, note any family history of pharyngitis, impetigo, perianal dermatitis, and GAS infections. If possible, family members should have a throat swab cultured for GAS. Ongoing vigilance against GAS infections in any of the patient’s close contacts is important, as symptom exacerbations have been reported following exposure to a sibling with GAS (even when the PANDAS patient had no evidence of infection). Prompt medical attention to symptoms suggestive of streptococcal infection is important not only to protect the patient, but also siblings, who may be at an increased genetic risk for PANS.

It is estimated that up to 16.5% of elementary school aged children present elevated SOR behaviors in the tactile or auditory modalities. However, this figure might represent an underestimation of Sensory Over Responsivity prevalence, since this study did not include children with developmental disorders or those delivered preterm, who are more likely to present it.

This figure is, nonetheless, larger than what previous studies with smaller samples had shown: an estimate of 5–13% of elementary school aged children.

Incidence for the remaining subtypes is currently unknown.

Because comorbid conditions are common with sensory integration issues, a person may have other conditions as well. People who receive the diagnosis of sensory processing disorder may also have signs of anxiety problems, ADHD, food intolerances, behavioral disorders and other disorders.