Psycogenic polydipsia is described as excessive water intake which is not appropirate to the homeostatic balance. We report a case of mild mental retardation with episodes of severe psychogenic polydipsia.

Prevalance of psycogenic polydipsia is %3,1 in mentally retarded patients (1). the case we present is unique because polydipsia is episodic, it is occuring after stressful life events and the patient has no comorbid psychotic or autism spectrum disorder.

We would like to inform about the good treatment response to olanzapine of this rare clinical phenomenon.

The patient who had first been referred to the internal medicine clinic for complaints of severe nausea, insomnia and fainting, was hospitalized in psychiatry department becuse of refusal to eat and vomiting. Details of the inpatient treatment, laboratory results and the follow up after hospitalization were analysed.

After the investigation, history of episodic polydipsia for 10 years is determined, with 3–4 episodes per year. He was drinking 25–30 lt of water a day during these episodes. all of the episodes were occuring after psychological stressors, including the death of his grandmother, grandfather and father.

Reactions of mentally retarded individuals to life stressors can be extremely different from normal. Olanzapine may be a treatment option in psychogenic polydipsia which is triggered with psychological stress.