Psychogenic Polydipsia in Primary Care

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: