History and exam

Key diagnostic factors

common

presence of risk factors

Strong risk factors include psychiatric disorders and neurodevelopmental disorders.

water-seeking and drinking

All patients have excessive or abnormal thirst, accompanied by intake of excessive quantities of water or fluid. Often noted by clinical staff or other observers.

Other diagnostic factors

common

agitation

Individuals with PPD often appear agitated at specific times each day prior to water loading and subsequent intoxication.

uncommon

polyuria

Has been noted in patients with polydipsia.[38]

headache

Symptom of hyponatraemia; typically, symptoms of hyponatraemia are often not evident unless an acute drop in serum sodium occurs.[41][42]

nausea or vomiting

Symptom of hyponatraemia; typically, symptoms of hyponatraemia are often not evident unless an acute drop in serum sodium occurs.[41][42]

Gastrointestinal symptoms (including nausea and vomiting) can be seen in patients with sodium levels between 125 and 130 mmol/L (125 and 130 mEq/L).

lethargy or confusion

Symptom of hyponatraemia; typically, symptoms of hyponatraemia are often not evident unless an acute drop in serum sodium occurs.[41][42]

Neurological symptoms are predominant at serum sodium levels <125 mmol/L (<125 mEq/L).[54]

seizures, delirium, or coma

Symptom of hyponatraemia; typically, symptoms of hyponatraemia are often not evident unless an acute drop in serum sodium occurs.[41][42]

Neurological symptoms are predominant at serum sodium levels <125 mmol/L (<125 mEq/L).[54]

Risk factors

strong

psychiatric disorders

PPD occurs in 6% to 20% of patients with psychiatric disorders but is most frequently seen in schizophrenia.[1][2][3][4][5][6][7] In a systematic review of hyponatraemia associated with excessive water intake in adults, 52% of people had a chronic psychiatric condition, most commonly schizophrenia spectrum disorders.[26]

Affective disorders, anxiety disorder, anorexia nervosa, obsessive compulsive disorder, and personality disorders have all been associated with PPD. PPD seen in adolescents and young adults is often associated with anorexia nervosa, possibly as a coping strategy and/or to reduce hunger.[13][14]

neurodevelopmental disorders

PPD has been noted in people with neurodevelopmental disorders, including autism spectrum disorder and Kleine-Levin syndrome. Prevalence was 3.5% in a survey of 877 inpatients with diagnoses including autism and personality/behaviour disorders.[15] A hospital population of 371 patients with developmental disabilities was found to have a prevalence of 6.2%.[16]

alcohol abuse

Small studies have found that alcohol abuse is more common amongst individuals with schizophrenia and PPD than in those without PPD. There also appears to be a correlation between severity of alcohol abuse and severity of PPD.[27][28]

weak

smoking

Nicotine stimulates antidiuretic hormone release. In some studies, up to 70% of patients with self-induced polydipsia were cigarette smokers.[18][19] In one study of psychiatric patients with compulsive water-drinking, symptomatic hyponatraemia developed only in those who were heavy smokers.[20]

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