New Perspectives on Comorbidity: Co-Occurring Major Mental and Substance Use Disorders in Public-Sector Psychiatric and Drug Treatment Patients

Barbara E. Havassy, Ph.D
University of California, San Francisco, School of Medicine, Department of Psychiatry

Background: The goal of this ongoing longitudinal study is to compare a sample of comorbid mental health treatment service users to a sample of drug treatment service users. Similarities across treatment users of these systems might argue for integration of services, while differences might support development of unique comorbidity treatment programs within systems. Findings reported here compare the prevalence of major mental and substance use disorders and levels of recent substance use. Comorbidity was defined as having a current major mental and substance use disorder. Method: The mental health system sample (MH) was recruited from four acute hospital diversion units and the drug treatment sample (DT) was recruited from three detoxification programs. All treatment settings were social model, acute crisis, short-term, residential programs. Participants were recruited soon after admission to the treatment settings and administered a study entry interview, including the Diagnostic Interview Schedule for DSM-IV (DIS-IV) and the Addiction Severity Index (ASI). Results: There were 106 MH and 120 DT comorbid participants. There were no significant differences between groups in prevalence of major psychiatric disorders (schizophrenia-spectrum, bipolar, depressive, and anxiety disorders). Nevertheless, differences between groups on schizophrenia-spectrum and bipolar disorders were marginally significant (p <.06), with DT compared to MH participants having lower rates of these disorders (31% vs. 43% and 20% vs. 31%, respectively) Of the substance use disorders examined (alcohol, amphetamine, cocaine, marijuana, and opiates), there were significant differences only on amphetamine and cocaine use disorders. DT participants compared to MH participants were less likely to meet criteria for amphetamine use disorders (15% vs. 26%, OR = 0.4, p<.04) and more likely to meet criteria for cocaine use disorders (70% vs. 56%, OR = 1.86, p<.03). With respect to substance use in the 30 days prior to treatment entry, DT participants were significantly more likely than MH participants to report drinking to intoxication (75% vs. 45%, OR = 3.6, p< .001), using cocaine (76% vs. 42%, OR = 4.4, p<.001), and opiates (42% vs. 26%, OR = 2.0, p<.02). They were also more likely to report more days of drug use (independent of drug) (99% vs. 80%, OR = 29.4, p<.001) and report more days of using more than one drug in a day (82% vs. 54%, OR = 3.8, p<.001). Nevertheless, among those who reported use there were no significant differences between groups in mean days of consumption. Conclusions: Despite certain differences between MH and DT comorbid participants, the most notable finding is the lack of differences. There were high prevalence rates of substance use disorders among MH participants, and of major mental disorders among DT participants. Furthermore, although more DT than MH participants reported recent substance use before treatment entry, among those who used, there were no significant differences in mean days of consumption. Significance: Although differences between groups should not be minimized, these findings indicate considerable similarities between comorbid MH and DT participants, and suggest that the integration of services in mental health and drug treatment systems where comorbid patients are encountered may be the most effective means of providing care.

Supported by NIH grant number R01DA10838.