Clinical Textbook of Addictive Disorders 3rd ed - R. Frances, S. Miller, A. Mack (Guilford, 2005) WW

252 IV. SPECIAL POPULATIONSsample of 222 Australian heroin injectors, half of whom were in methadonetreatment, and found that they had used a mean of 5.3 different classes of substancesin the prior 6 months, and 40% had three or more current DSM-III-Rdependence diagnoses. Injecting drugs increases the risk for comorbid substancedependence. Dinwiddie and colleagues (1996) found elevated lifetime rates ofalcohol, amphetamine, sedative/hypnotic opiate and hallucinogen dependenceamong injecting drug users (IDUs) compared to non-IDUs with a substantialdrug use history.Severity of psychopathology also appears to be highly associated with multiplesubstance use. Compared to users of cocaine alone, compulsive simultaneoususers of cocaine and heroin (“speedball”) have higher Minnesota MultiphasicPersonality Inventory (MMPI) scores on depression and trait anxiety, with moresevere psychopathology (Malow, West, Corrigan, Pena, & Lott, 1992). With frequentuse of this combination, cocaine abusers who are using opiates to reduce thejitters and “crash” of intravenous cocaine use likely increase the risk of heroindependence in this population (Levin, Foltin, & Fischman, 1996).Darke and Ross (1997) demonstrated in a sample of Australian heroininjectors that heroin use is correlated strongly with not only multiple substanceuse but also comorbid psychiatric disorders. Among IDUs, the extent and severityof non-substance-related psychopathology is a strong and linear predictor ofthe extent of multiple substance dependence. The prevalence of current moodand/or anxiety disorders was about 55%, with 25% having both a current moodand anxiety disorder—in each case, clearly greater than prevalence in the generalpopulation (Darke & Ross, 1997; Kessler et al., 1994). Darke and Ross alsofound a significant positive correlation between the number of lifetime drugdependence diagnoses and the number of lifetime comorbid psychiatric diagnosesin IDUs, and a similar positive correlation (p