The purpose of this study was to test a theoretical framework that proposed a relationship between severe psychiatric symptoms and self-induced water intoxication (SIWI) by using reliable and valid measures. Twenty of 28 community-dwelling individuals with severe mental illness (SMI) in the sample exhibited excess fluid consumption as reflected by a mean urine specific gravity of 1.003 mEq/L. The psychometric measures included the Positive and Negative Syndrome Scale (PANSS), the Self Deficit Syndrome Scale (SDSS), and the Spielberger State-trait Anxiety Scale (STAI From X-1). A significant relationship was found at p .01 between severity of psychotic symptoms and severity of SIWI and between severity of SIWI and psychopathology symptoms within the PANSS. Anxiety was higher in those with SIWI before fluid loading compared with those with less excess fluid intake (i.e., USG < 1.010), and anxiety decreased from morning to evening in those with SIWI compared with those who did not exhibit excess fluid intake. The findings revealed a strong relationship between SIWI and severe psychiatric symptoms, including psychosis and a broad range of psychiatric symptoms. The findings provided initial support for the proposed theory, and consideration needs to be given to the development of interventions to augment existing treatment of fluid control.