High levels of multimorbidity exist among patients entering treatment for alcohol and other drug use. As a result, clinicians must examine individuals’ psychopathology thoroughly to provide the most complete and effective treatment possible, according to a study published in the Journal of Substance Abuse Treatment.
“The co-occurrence of mental and substance use disorders has important clinical implications: In addition to presenting with a more complex array of problems, clients with co-occurring disorders are at risk of poorer outcomes following treatment,” wrote lead author Karen Urbanoski, Ph.D., of the Centre for Addiction and Mental Health in Toronto, and her associates. “The clustering of multiple disorders within individuals highlights the cumulative burden of psychopathology, constituting one aspect of illness severity,” they added (J. Subst. Abuse Treat. 2015;49:21-6).
To conduct the study, Dr. Urbanoski and her associates recruited 544 adults from three southwest Ontario outpatient addiction treatment clinics. Most of the participants were male (68%), and the average age was 37. In the year before treatment, the most commonly used substances were alcohol (91%), cocaine (63%), cannabis (63%), prescription opioids (36%), and benzodiazepines (27%).
The investigators administered the Psychiatric Diagnostic Screening Questionnaire (PDSQ) for DSM-IV Axis 1 disorders to each patient for completion at treatment admission. Latent class analyses were used to identify and classify subjects who presented with specific patterns of co-occurring mental disorders, with three distinct classes ultimately created for the purposes of this study: no comorbidity (in other words, substance use disorders [SUD] only); co-occurring major depression; and multimorbidity, or a high degree of psychopathology.
The SUD cohort was found to contain 54.6% of patients, while 37.4% fell into the co-occurring major depression classification, and 8% were designated as multimorbidity. Patients who were older had less likelihood of being classified with co-occurring major depression, women were more likely than men to be in the multimorbid class, and individuals who were married or partnered had a lower risk of being in either of the comorbid classes.
“Unlike studies conducted in general population samples, classes characterized by little or no psychopathology or pure internalizing disorders do not apply in this instance, because of the uniform presence of SUD,” wrote the authors. They added: “With the uniform presence of SUD in this sample, one interpretation of these results is that they identify not clusters of disorders, but levels of severity of internalizing symptoms. Most conditions were moderately to highly correlated with the others, and the prevalence of disorders rises consistently across classes.”
Dr. Urbanoski and her associates cited several limitations. One is that the PDSQ is a self-reported questionnaire. In the addition, assessments for all DSM-IV disorders – including bipolar disorder – are not included on the questionnaire. Axis 2 disorders and impulse control disorders are also not included on the PDSQ.
The study was supported by a research award from the Canadian Institutes for Health Research. The authors reported no relevant financial disclosures.