Primary polydipsia and psychogenic polydipsia are forms of polydipsia characterised by excessive fluid intake in the absence of physiological stimuli to drink. Psychogenic polydipsia which is caused by psychiatric disorders, often schizophrenia, is often accompanied by the sensation of dry mouth. Some forms of polydipsia are explicitly non-psychogenic. Primary polydipsia is a diagnosis of exclusion. Signs and symptoms
Signs and symptoms of psychogenic polydipsia include:
Excessive thirst and xerostomia, leading to overconsumption of water
Hyponatraemia, causing headache, muscular weakness, twitching, confusion, vomiting, irritability etc., although this is only seen in 20% – 30% of cases. Hypervolemia, leading to oedema, hypertension and weight gain (due to the kidneys being unable to filter the excess blood) in extreme episodes
Tonic-clonic seizure
Behavioural changes, including fluid-seeking behaviour; patients have been known to seek fluids from any available source, such as toilets and shower rooms.The most common presenting symptom is tonic-clonic seizure, found in 80% of patients. Psychogenic polydipsia should be considered a life-threatening condition, since it has been known to cause severe hyponatraemia, leading to cardiac arrest, coma and cerebral oedema. Brain differences
Psychogenic polydipsia in individuals with schizophrenia is associated with differences seen in neuroimaging. MRI scans may be used to help with differentiating between PPD and diabetes insipidus, such as by examining the signal of the posterior pituitary (weakened or absent in central DI). Some patients, most often with a history of mental illness, show a shrunken cortex and enlarged ventricles on an MRI scan, which makes differentiation between psychogenic and physiological cause difficult.
taking small sips of water, having ice cubes instead of drinks) in addition to challenging delusions leading to excessive drinking.Psychogenic polydipsia often leads to institutionalisation of mentally ill patients, since it is difficult to manage in the community. Most studies of behavioural treatments occur in institutional settings and require close monitoring of the patient and a large degree of time commitment from staff. Pharmaceutical
A number of pharmaceuticals may be used in an attempt to bring the polydipsia under control, including:

Atypical antipsychotics, such as clozapine, olanzapine and risperidone
Demeclocycline, a tetracycline antibiotic, which is effective due to the side effect of inducing nephrogenic diabetes insipidus. Demeclocycline is used for cases of psychogenic polydipsia, including those with nocturnal enuresis (bed-wetting). Its mechanism of action involves direct inhibition of vasopressin at the DCTs, thus reducing urine concentration.There are a number of emerging pharmaceutical treatments for psychogenic polydipsia, although these need further investigation:
ACE Inhibitors, such as enalapril
Clonidine, an alpha-2 adrenergic agonist
Irbesartan, an angiotensin II receptor antagonist
Propranolol, a sympatholytic beta blocker
Vasopressin receptor antagonists, such as conivaptan
Acetazolamide, a carbonic anhydrase inhibitorLithium was previously used for treatment of PPD as a direct competitive ADH antagonist, but is now generally avoided due to its toxic effects on the thyroid and kidneys.It is important to note that the majority of psychotropic drugs (and a good many of other classes) can cause dry mouth as a side effect, but this is not to be confused with true polydipsia in which a dangerous drop in serum sodium will be seen.