ASSESSMENT

Several common difficulties arise when assessing substance disorders among persons with severe mental illness (Drake et al. 1993a; Drake and Mercer-McFadden 1995; Stone et al. 1993). The most common problem is that mental health clinicians often do not obtain a thorough history of substance use (Ananth et al. 1989). Even when interviewed thoroughly, however, persons with dual disorders are subject to the usual problems of denial, distortion, and minimization that attend self-reports of substance use, especially the use of illicit drugs, in the general population (Aiken 1986; Galletly et al. 1993; Stone et al. 1993). Psychiatric clients are also prone to individual distortions arising from the cognitive, emotional, and other aspects of their mental illness (Mueser et al. 1992).

Another important factor that complicates assessment is the fact that the usual dimensions of substance abuse—pattern, consequences, dependence syndrome, and subjective distress—are qualitatively different in substance abusers who have mental illness compared to those who do not (Drake et al. 1990; Lehman et al. 1994; McHugo et al. 1993). Specifically, compared with non-mentally ill substance abusers, those with dual disorders use lower amounts of alcohol and drugs, experience different consequences, are less likely to develop a dependence syndrome, and have less subjective distress. For example, the typical consequences of substance abuse among people with a mental disorder are difficulties with money management, destabilization of illness, unstable housing, and inability to participate in rehabilitation, but not with the items on the Michigan Alcohol Screening Test (Selzer 1971) or the Alcohol Dependence Scale (Skinner and Horn 1984). Standard instruments, such as the Addiction Severity Index (McLellan et al. 1980), are relatively insensitive to clinically important levels of abuse among persons with psychiatric disorders. One last but critical problem is that dual-disordered clients are typically in a premotivational state regarding their substance abuse, even if they are well engaged in mental health treatment (Drake et al. 1990). To be useful for treatment planning and monitoring, assessment instruments must be sensitive to stages of motivation and to changes that occur prior to attaining abstinence. The authors and others, thus, recommend the use of multiple tests (Carey, this volume; Drake et al. 1990), multimodal testing (Stone et al. 1993), and an explicit assessment of the stage of treatment (McHugo et al. 1995). Furthermore, there is a need to develop new instruments sensitive to the presence of substance use disorders in the population of persons with severe psychiatric disorders (Drake et al. 1993a; Lehman et al. 1993b).