Psychogenic Polydipsia (PPD)—also known as primary polydipsia—is a psychiatric condition marked by excessive, voluntary water intake in the absence of physiological thirst stimuli. Patients often consume >4 L/day, driven by compulsive behaviours rather than metabolic need. It is most commonly associated with schizophrenia, where it affects an estimated 11–20% of patients, but may also occur in those with anxiety, personality disorders, or intellectual disability.

Though it may seem benign, PPD carries a significant risk of complications:

• Hyponatraemia due to dilutional ↓Na⁺

• Cerebral oedema, seizures, confusion

• Rarely, coma or death

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For GPs, early recognition is key, as PPD can mimic more common conditions such as diabetes mellitus (DM) or diabetes insipidus (DI). Primary care plays a crucial role in identifying at-risk patients, ruling out organic causes, and coordinating multidisciplinary psychiatric input.

Pathophysiology and Mechanisms

The underlying cause of psychogenic polydipsia (PPD) is not fully understood, but is believed to involve multiple interacting factors:

Mechanism	Explanation
Dopaminergic Dysfunction	↑ Dopamine (esp. D2 receptors) may overstimulate thirst centres in the lateral hypothalamus. Linked with schizophrenia.
Osmotic Dysregulation	Possible "reset osmostat" alters the set point for AVP (arginine vasopressin) release → impaired water excretion despite hypo-osmolality.
Medication Effects	Dry mouth from anticholinergic psychotropics may ↑ fluid intake. Some drugs also a

Presentation of Psychogenic Polydipsia

Patients with psychogenic polydipsia (PPD) typically present with excessive thirst and compulsive water drinking, often consuming liters of fluid daily without a physiological trigger. The hallmark symptom is frequent urination (polyuria) with dilute urine, as the body attempts to excrete the excess water. Individuals may report drinking water excessively due to psychological urges, often linked to psychiatric conditions like schizophrenia, schizoaffective disorder, or anxiety disorders.

Presentation Aspect	Details & Physiological Explanation
Excessive Thirst (Polydipsia)	Patients often consume >4 L/day. Thirst is not driven by true dehydration or osmolality changes but by psychiatric compulsion.
Frequent Urination (Polyuria)	High fluid intake overwhelms renal concentrating ability → dilute urine (↓ urine osmolality), frequent voiding.
Water-Seeking Behaviour	Often habitual or compulsive; patients may deny excess intake or view it as soothing. Common in schizophrenia or anxiety disorders.
Hyponatraemia Symptoms	Excess water dilutes serum sodium (Na⁺ <135 mmol/L) → cellular swelling → headache, confusion, nausea, seizures, coma in severe cases.
Onset & Detection	Often detected during psychiatric assessment or investigation of low Na⁺. May mimic DM or DI on initial presentation.
Physical Examination	Usually unremarkable unless ↓Na⁺ is severe. Look for signs of neurological involvement (e.g. altered mental status).

Clinical Significance in Primary Care

Primary care clinicians should maintain high index of suspicion for psychogenic polydipsia (PPD) in psychiatric patients—especially when presenting with:

• Excessive thirst or compulsive water intake

• ⚠Signs of hyponatraemia: headache, nausea, confusion, lethargy

• Unexplained neuropsychiatric symptoms

• ⚡ Seizures in patients with known psychiatric illness

Management Overview

Management of psychogenic polydipsia (PPD) focuses on preventing complications (especially hyponatraemia) and addressing the underlying psychiatric disorder:

• Treat underlying psychiatric condition: Optimise antipsychotic therapy (e.g. consider clozapine in refractory cases). Avoid medications that worsen dry mouth or AVP dysregulation.

• Fluid restriction: Essential to prevent water intoxication. May require supervised intake in severe cases.

• Behavioural interventions: Cognitive-behavioural therapy (CBT), psychoeducation, and routine setting can reduce compulsive drinking.

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• Monitor serum sodium regularly—especially during changes in mental state or fluid intake.

• Multidisciplinary care: Involves GPs, psychiatrists, nurses, and carers. Crucial for long-term adherence and safety.

• Urgent referral: Needed for patients with Na⁺ <125 mmol/L, seizures, or neurological signs.

Primary care plays a vital role in early recognition, baseline investigations, and ongoing monitoring, ensuring safe and coordinated care.

References

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5. Zdanowicz M, et al. Polydipsia and hyponatremia in psychiatric illness: mechanisms and management. Front Psychiatry. 2023. Full Text

6. de Leon J. Polydipsia in Schizophrenia: an Overview. Psychiatry (Edgmont). 2007. PMC

7. Verbalis JG. Disorders of body water homeostasis. J Clin Invest. PubMed

8. Balzan R, et al. Primary polydipsia: diagnosis and management. The Carlat Psychiatry Report. PDF

9. Clinical Guidelines. Water Deprivation Test in Adults. North Bristol NHS Trust. PDF

10. Makhoul IR, et al. Severe symptomatic hyponatremia due to psychogenic polydipsia. JAMA Intern Med. JAMA

11. Carlat Report Podcast. Management of Psychogenic Polydipsia. Transcript

12. GP Notebook. Psychogenic and Primary Polydipsia. GP Notebook

13. UPMC Physician Resources. Screening for Diabetes Insipidus. UPMC

14. NIH Case Reports. Hyponatremia Secondary to Psychogenic Polydipsia. Cureus. Article

15. European Journal of Endocrinology. Diagnostic testing in polyuria-polydipsia syndrome. EJE

16. Front Psychiatry. Understanding AVP dynamics in primary polydipsia. PMC