A number of my colleagues and I recently completed a study based on the fact that individuals with co-occurring mental and substance use disorders have increased rates of mortality in relation to the overall population. We were struck by the fact that studies until now have shown what the relationship between measures of treatment quality and mortality for these individuals is.
Consequently, we were led to focus on a single objective: to examine the association between a number of quality measures and mortality based on a range of one to two years.
Design, setting and participants: To conduct the survey, we focused on a number of patients with co-occurring mental illness — including but not limited to such illnesses as schizophrenia, bipolar disorder and major depression — also suffering from substance use disorders.
We used the latest techniques such as logistic regression models to examine the association between one- to two-year mortality and various quality measures, while risk-adjusting for patient characteristics. Quality measures included receipt of psychosocial treatment, receipt of psychotherapy, treatment initiation and engagement, and a measure of continuity of care. We also examined the relationship between number of diagnosis-related outpatient visits and mortality, and conducted sensitivity analyses to examine the robustness of our findings to an unobserved confounder.
Results: All measures except for treatment engagement at 24 months were significantly associated with lower mortality at both 12 and 24 months. At 12 months, receiving any psychosocial treatment was associated with a 21% decrease in mortality; psychotherapy, a 22% decrease; treatment initiation, a 15% decrease, treatment engagement, a 31% decrease; and quarterly, diagnosis-related visits a 28% decrease. Increasing numbers of visits were associated with decreasing mortality. Sensitivity analyses indicated that the difference in the prevalence of an unobserved confounder would have to be unrealistically large given the observed data, or there would need to be a large effect of an unobserved confounder, to render these findings non-significant.
This study had a number of conclusions and of particular relevance. It is the first study to show an association between process–based quality measures and mortality in patients with co-occurring mental and substance use disorders, and provides initial support for the predictive validity of the measures.
If you would like more information on co-occurring disorders, please visit my website. There you will find a number of downloadable PDFs with the complete text of the research.
Katherine Watkins, M.D. is a psychiatrist with offices in West Los Angeles on the border of Santa Monica.
