POLYDIPSIA IN ADULTS WITH LEARNING DISABILITIES: PREVALENCE, PRESENTATION AND AETIOLOGY

Polydipsia can be defined as the ingesting of excessive quantities of non-alcoholic fluid. Differentiation is made between primary polydipsia (excessive drinking for which there is no identifiable physiological need or stimulus) and secondary polydipsia (drinking related to thirst or homeostatic needs) (Johnson et al., 1985). No formalised diagnostic criteria for polydipsia exist, with resultant ambiguity within terminology used and definition of excessive drinking. Terms such as ‘compulsive water drinking’ (Deb et al., 1994; Chinn, 1974; Lee et al., 1989; Noonan and Ananth, 1977), ‘psychogenic polydipsia’ (Viewing et al., 1985; Hariprasad et al., 1980), and ‘psychosis-intermittent hyponatraemia-polydipsia syndrome’ (PIP) (Viewing et al., 1986) have been used synonymously with polydipsia; however, each indicates certain elements of the condition that may not necessarily exist. The phenomenon of water intoxication has also been confused with polydipsia; however, they exist as clearly distinct though related conditions (Cooney, 1989). Polydipsic episodes may develop into