Psychogenic Polydipsia (Primary Polydipsia)

How psychogenic polydipsia leads to water intoxication

Healthy kidneys can excrete a large volume of water a day, often in the range of 10 to 15 liters, by making very dilute urine. Problems arise when:

• intake exceeds the kidneys' capacity
• the person eats little salt or protein, which lowers the kidneys' ability to excrete water (as in "tea and toast" diets)
• antidiuretic hormone (ADH) is released inappropriately, for example due to psychosis, stress, nausea, smoking or medicines

When water builds up, blood sodium falls (hyponatremia). Water moves into brain cells, which swell inside the skull, causing neurological symptoms.

Who is at risk

• people with schizophrenia and other psychotic disorders, especially in long-term care
• bipolar disorder and severe depression
• people with intellectual disability or autism
• eating disorders such as anorexia nervosa, where water is used to suppress appetite or alter weight
• anxiety and compulsive behaviors
• smokers, because nicotine stimulates ADH

Medicines can add to the problem: antipsychotics and anticholinergics cause dry mouth and thirst, while some antidepressants, carbamazepine and other drugs cause the body to hold on to water.

Possible reasons for excessive drinking

• delusions, such as beliefs that water purifies the body
• relieving anxiety or as a compulsive habit
• dry mouth from medicines
• a disturbed thirst mechanism in the brain

Symptoms

Of excessive drinking

• drinking large volumes, sometimes from any available source
• frequent urination, including at night
• very pale, clear urine
• weight gain over the day that falls overnight

Of low sodium (hyponatremia)

• headache
• nausea and vomiting
• tiredness and muscle cramps
• unsteadiness and falls
• confusion, irritability and worsening psychiatric symptoms
• seizures and coma in severe cases

Diagnosis

Doctors distinguish psychogenic polydipsia from other causes of excessive thirst and urination:

Tests may include:

• blood sodium and osmolality, glucose, calcium, potassium and kidney function
• urine osmolality and sodium: very low urine osmolality (often under 100 mOsm/kg) suggests excess water intake
• daily weights and fluid charts
• a carefully supervised water deprivation test or copeptin-based testing to rule out diabetes insipidus

Treatment

Severe hyponatremia

Hospital treatment is needed for seizures, confusion or very low sodium. Doctors may give small amounts of concentrated (hypertonic) saline and closely limit how quickly sodium rises, because correcting too fast can cause a serious brain injury called osmotic demyelination. When water intake stops, the kidneys often excrete the excess quickly, so sodium is monitored frequently.

Ongoing management

• fluid restriction with a daily target agreed with the care team
• weight monitoring: weighing several times a day can detect excess intake early; a set weight gain triggers fluid restriction
• behavioral approaches: education, reinforcement, structured activities, cognitive behavioral strategies
• managing dry mouth: sugar-free gum, ice chips in measured amounts, saliva substitutes
• reviewing medicines that cause dry mouth or water retention
• treating the underlying psychiatric condition; clozapine has been reported to reduce polydipsia in some people with schizophrenia
• adequate salt and protein intake under medical guidance

Complications

• seizures, brain swelling, coma and death from hyponatremia
• falls and injuries
• bladder enlargement, urinary retention and kidney swelling from chronic high urine volumes
• osteoporosis
• heart failure in people with existing heart disease

Frequently asked questions

What is psychogenic polydipsia?

Psychogenic polydipsia is drinking excessive amounts of water without a physical need, usually linked to a psychiatric condition such as schizophrenia. It can lead to dangerously low blood sodium, known as water intoxication.

How much water is too much?

Healthy kidneys can usually excrete around 10 to 15 liters a day, but the safe amount varies with diet, medicines and health. Drinking several liters in a short time, especially with little food or salt, can overwhelm the kidneys and lower sodium.

What are the symptoms of water intoxication?

Early symptoms include headache, nausea, vomiting, tiredness and muscle cramps. As sodium falls further, people become confused, unsteady and drowsy, and may have seizures or lose consciousness. Severe cases are a medical emergency.

How is psychogenic polydipsia different from diabetes insipidus?

In psychogenic polydipsia, drinking too much water is the primary problem, and urine is dilute because of the excess intake. In diabetes insipidus, the body loses too much water in the urine, causing thirst. Blood sodium tends to be low in polydipsia and normal or high in diabetes insipidus.

How is psychogenic polydipsia treated?

Treatment includes supervised fluid restriction, regular weight checks, behavioral strategies, managing dry mouth, reviewing medicines and treating the underlying mental health condition. Severe low sodium needs careful hospital treatment.