Prevalence of mental illness in the general community The National Survey of Mental Health and Wellbeing of Adults (Australian Bureau of Statistics 1997) found that 18% of Australians had a mental illness at some point during the 12-month period prior to survey completion. Mental illness was diagnosed with a computerised version of the Composite International Diagnostic Interview (CIDI). The National Survey of Mental Health and Wellbeing of Adults (Andrews et al 1999) estimated that at some time during a year 1,300,000 adults over 18 years of age have an anxiety disorder, 1,042,000 a substance abuse disorder and 779,000 an affective disorder. It is important to note that 62% of those with a mental disorder do not access mental health services (Australian Bureau of Statistics 1997). Therefore, general health care settings provide an opportunity for detection and intervention for clients with a mental illness, who would not otherwise receive treatment.