Seasonal stability of water balance among schizophrenic patients subject to water intoxication.

1. Diurnal weight gain, afternoon hyponatremia, and polyuria were assessed for one year among eight male schizophrenics subject to water intoxication. 2. The authors normalized the diurnal weight gain (NDWG) as a percentage by subtracting the 7 a.m. weight from the 4 p.m. Weight, multiplying the difference by 100, and then dividing the result by the 7 a.m. weight. 3. NDWG ranged between 2.69 +/- .99 and 3.34 +/- 1.32 percent (F [3, 5] = .885, p = .509) during the four seasons of the year. 4. The seasonal decrease in afternoon serum sodium compared to its morning counterpart ranged between 4.23 +/- 1.96 and 6.14 +/- 2.82 mmol/l (F [3, 5] = 2.212, p = .205). 5. Seasonal polyuria ranged between 8.2 +/- 3.5 and 8.8 +/- 3.2 liters (F [3, 5] = .228, p = .873). 6. Among schizophrenics subject to water intoxication, the seasonal stability in our three parameters of water imbalance suggest they may be used to follow patients with altered water homeostasis over time. This finding has both clinical and research implications.