A Case of Psychogenic Polydipsia in an Elderly: An Overlooked Diagnosis

Primary polydipsia, or psychogenic polydipsia, is characterised by excessive fluid intake without an underlying physiological cause. If left untreated, primary polydipsia may result in life-threatening hyponatremia and can lead to complications such as nausea, vomiting, confusion and seizure episodes, potentially becoming life-threatening if not recognised and managed early. The aetiology of this condition is incompletely understood and is frequently attributed to psychiatric disorders, most commonly chronic schizophrenia. Psychogenic polydipsia occurs in up to 20% of psychiatric patients, and this case serves as a reminder to be cognisant of water overconsumption. This case report presents a 74-year-old male with a three-year history of excessive thirst and polyuria, which worsened following the death of his elder brother. Laboratory investigations showed normal random blood sugar and HbA1c levels, normal renal and liver function tests and mild hyponatremia, while radiological investigations were grossly normal. Ultimately, a water deprivation test ruled out diabetes insipidus, leading to a diagnosis of primary polydipsia. The patient was started on oral medication and psychotherapy after diagnosis, and he improved significantly with treatment. He was discharged on oral atypical antipsychotics, with water restriction and regular psychotherapy sessions for further improvement. This case highlights the importance of a thorough diagnostic evaluation of excessive thirst in elderly patients and the necessity of initiating appropriate treatment, which can prevent complications such as severe dilutional hyponatremia in this population.