Background: Major depression makes an important contribution to disease burden in Canada. In principle, the burden of major depression can be reduced by the provision of treatment within the health care system. In a previous data analysis, the National Population Health Survey (NPHS) reported an increase in antidepressant (AD) use between 1994 and 1998. In this paper, the analysis is extended to 2000, and additional aspects of health care utilization are described.Methods: The NPHS provides a unique source of longitudinal data concerning major depression and its treatment in Canada. In this survey, probable cases of major depression were identified using a brief predictive instrument; health care utilization was evaluated using additional survey items; and the latest data release from Statistics Canada (that is, 2000) was used to make weighted estimates of the frequency of health care utilization in relation to major depression status.Results: The use of ADs has continued to escalate. These increases have been largest in men and in persons aged under 35 years. There has been an increase in polypharmacy: in 2000, almost 9% of persons taking an AD reported taking more than 1 AD medication-a tripling since 1994. The frequency of consultations with alternative practitioners has also grown. Although the overall proportion of persons with major depression who report consulting with health professionals about their mental health has not increased, the number of persons with major depressive disorder reporting 6 or more visits to nurses, social workers, and psychologists may have.Conclusion: The provision of AD treatment continues to expand in Canada. This probably represents a changing pattern of practice, because the frequency of professional consultation has not increased. More detailed data are required to evaluate the extent to which treatment needs are being met. [ABSTRACT FROM AUTHOR]