Community surveys over the last 30 years have established that people with mental disorders have increased risks of substance use disorders (Grant et al., 2009, Regier et al., 1990 and Teesson, Slade & Mills, 2009), with these risks being especially high in schizophrenia and bipolar disorder (Grant et al., 2009, Kavanagh et al., 2004, Koskinen et al., 2009 and Volkow, 2009). Not only is substance use common: it also has significant symptomatic and functional impacts, particularly in serious mental disorders (Hides, Dawe, Kavanagh, & Young, 2006). Research on psychological treatments for these comorbidities is still at a relatively early stage, requiring both replications, improvements in impact and maintenance, and dismantling of effective components (Kavanagh & Mueser, 2007). However, there is now substantial evidence to guide treatment design, including the need for treatment integration and for the use of motivational interviews (Kavanagh & Connolly, 2009). It is therefore imperative that people with these comorbid disorders are detected and that attempts are made to address their problems.
Without systematic screening, current substance use disorders are frequently missed by treating clinicians (Appleby, Dyson, Luchins, & Cohen, 1997). In the last 20 years, a range of brief screening measures for substance misuse in people with mental disorders has been developed (Agelink et al., 1999, Barry et al., 1995, Brown et al., 2001, Carey et al., 1997, Maisto et al., 2000, Rosenberg et al., 1998, Searles et al., 1990 and Wolford et al., 1999), which has demonstrated varying levels of utility.
The Severity of Dependence Scale (SDS; Gossop et al., 1995) is a reliable measure of dependence on heroin, amphetamines and cocaine (Dawe, Loxton, Hides, Kavanagh, & Mattick, 2002) that shows significant correlations with behavioural indices of dependence, including dose, frequency and duration of use (Darke, Ross, & Hall, 1996). Its utility as a screen for cannabis dependence in the general population is less well established (Swift, Copeland, & Hall, 1998). The SDS has demonstrated both internal consistency and validity as a screen for cannabis dependence in a sample with psychosis (Hides, Dawe, Young, & Kavanagh, 2007). Testing of its applicability to other substances is needed.
The Alcohol Use Disorders Identification Test (AUDIT; Saunders, Aasland, Babor, De La Fuente, & Grant, 1993) is a screen for alcohol problems that has substantial international data on its efficacy in general population samples. Its strength (relative to competing measures) is its relative sensitivity to mild to moderate alcohol problems, while retaining an ability to also identify people with more severe ones. In previous studies of people with serious mental disorders (Dawe et al., 2000 and Maisto et al., 2000), the standard cutoff of 7/8 on the AUDIT has shown high levels of sensitivity (87–90%), but varying levels of both specificity (70–90%) and correct classification (73–89%). Further testing in people with serious mental disorders is required.
A gap in the existing repertoire of commonly used screening measures is one that provides an assessment of the functional impact of any one selected substance and is applicable to people with severe mental disorders. Such a measure would potentially be of significant value, not only as a screen for a specific substance use disorder, but also as a basis for motivational interviews that focused on that substance (Miller & Rollnick, 1991).
The primary aim of the current paper was to develop such a measure, the DrugCheck Problem List (PL). A secondary aim was to obtain further data on the performance of the SDS and the Australian version of the AUDIT as screens for substance misuse in people with psychosis, and compare their performance with that of the DrugCheck.
Study 1 describes an initial examination of the psychometric characteristics of the PL, and its comparison with the SDS and Aus-AUDIT as a predictor of DSM-IV substance use disorders. The study combined two samples of inpatients with psychoses—a group at an early episode, and a forensic sample. This combination provided a sufficiently large and diverse sample for the preliminary test of the internal structure and predictive validity of the PL. In Study 2, a confirmatory factor analysis was undertaken on the PL, and its positive predictive value was checked in a new and larger sample of inpatients with psychosis.
