Introduction: Increased water intake and output is more common among psychiatric patients than in the general population, especially for patients with schizophrenia. Animal studies suggest that polydipsia and polyuria derive, in part, from dopamine dysregulation. Stimulated by these observations this study sought to elucidate relationships among water homeostasis, monoamine metabolism, and electrolyte excretion in schizophrenic patients with and without paranoid hallucinatory symptoms (PH vs. NP), thought to reflect hyper- and hypo-dopaminergic states respectively, and to compare these with those shown by patients with obsessive compulsive disorder (OCD).

Methods: 24hr-urine samples for electrolyte, monoamine and metabolite measures were taken from 14 schizophrenic patients with PH symptoms, 13 with predominantly nonparanoid (NP) symptoms, 11 OCD patients and 27 healthy controls (matched for age, weight and creatinine production). Water intake and serum electrolytes was sampled during 3-4 hours of psychological testing.

Results: 1. PH patients drank 2-3 times more than the others, yet 24hr-urinary volumes were 75% larger in both PH and NP patients than in the two comparison groups. 2. Daily potassium excretion was a bit higher in PH patients, but concentrations of sodium, potassium and phosphate tended to be lower in PH and NP patients than in the others. 3. Positive associations of electrolytes with homovanillic acid excretion were consistent across groups and not directly related to medication. 4. But associations of electrolyte excretion with noradrenergic activity in controls were absent in psychotic patients and associations with serotonin in OCD patients were absent in the other groups.

Conclusions: Increased water intake and output in PH patients (i.e. poor water homeostasis) along with the disturbed association with noradrenergic metabolism (more MHPG excretion) are consistent with increased autonomic activity in these patients. The independence of measures of water homeostasis from dopaminergic medication indicates that the associations in clinically responding PH patients of polydipsia with DA function (decreased DA levels) may be pertinent to this subgroup but not to schizophrenia in general