Persistent hazardous users experienced poorer outcomes in the domains of social functioning and psychiatric symptomatology, including depression, than intermittently hazardous or nonhazardous users. The evidence suggests that among people with co-existing psychiatric and substance use disorders, persistent hazardous substance users had poorer outcomes than intermittent hazardous substance users or non-hazardous users. These results highlight the need to establish more assertive, effective, and integrated services and associated health policies. The findings were viewed as complex with future research highly recommended in clarifying the position. Research has shown that people with a mental illness are at a greater risk of developing substance use disorders compared to the general population and people with substance use disorders have a higher incidence of psychiatric problems than the general population. There have been few longitudinal studies assessing the natural history of drug use patterns in patients with co-existing psychiatric and substance use disorders or their long-term outcomes. This longitudinal study of research conducted between 1996 and 1998 sought to document long-term patterns of substance use among people with co-existing psychiatric and substance use disorders and to explore the different psychosocial outcomes for the resulting substance use groups (persistent hazardous, intermittent hazardous, and nonhazardous users). Forty patient participants from the original study completed assessments which included measures of demographic, characteristics, substance use, criminality, social dysfunction, psychiatric symptomatology and depression. Tables, references