Psychogenic polydipsia in intellectual disability – A clinical challenge

Abstract

Introduction: Primary polydipsia (PP), or psychogenic polydipsia, is the excessive liquid intake (> 3 litres per day) that is not explained by any other medical condition. It can occur in up to 14% of psychia- tric patients and the origin of the water-seeking behaviour among these patients remains unknown. When uncontrolled, patients drink beyond their renal capacity of excretion, developing hyponatremia, which can progress to water intoxication with nausea, vomiting, confusion, ataxia and can even be fatal. Methods: Case presentation based on the observation of the patient in the inpatient unit, analytical studies and the patient’s cli- nical records. We present a non-systematic review of the literature on the possible mechanisms that may be at the origin of the primary polydipsia and treatment approaches that have been suggested. Case presentation: We present a case of an individual with an intellectual disability medicated with risperidone for several years suffering from primary polydipsia and consequent severe water in- toxication. After stopping risperidone and switching to low dose clo- zapine, the polydiptic behaviour stopped. One month after discharge it hadn’t resurged and the patient remained analytically normal. Discussion: Antipsychotics have been suggested to be asso- ciated with primary polydipsia due to their high affinity to dopamine D2 receptors with consequent receptor hypersensitivity in the hypo- thalamic-pituitary-adrenal axis and centre of thirst. Fluid restriction is important to correct hyponatremia. A pharmacological approach is often imperative to help patients to become more permeable to behavioural strategies. Unlike other antipsychotics, clozapine does not induce D2 hypersensitivity in the centre of thirst, therefore, it can be a reasonable treatment option. Conclusion: It is important to elucidate clinicians about this condition since it is common in psychiatric patients and often goes unnoticed or inadequately approached. Further investigations on the link between primary polydipsia and mental diseases are needed, as they are greatly under-researched, in order to find new treatments and management approaches to this condition.

Keywords

• Primary Polydipsia
• Psychogenic Polydipsia
• Intellectual Disability
• Water Intoxication
• Antipsychotics
• Clozapine