Administration and Policy in Mental Health, Vol. 30, No. 1, September 2002 ( 2002) SYMPTOM SEVERITY, AMOUNT OF TREATMENT, AND 1-YEAR OUTCOMES AMONG DUAL DIAGNOSIS PATIENTS Christine Timko and Rudolf H. Moos ABSTRACT: This study reports on associations among symptom severity, amount of treat- ment, and 1-year outcomes in a national sample of 8,622 dual diagnosis patients, who were classified at treatment entry into low-, moderate-, and high-severity groups. Patients with more severe symptoms at intake had poorer 1-year outcomes. Higher severity patients did not receive adequate “doses” of care: Compared with low-severity patients, they had a shorter duration of care, although a longer duration was associated with improved out- comes; they also were less likely to receive outpatient substance abuse treatment, although more intensive treatment was associated with better drug outcomes. High-severity patients improved more on drug and legal outcomes, but less on psychiatric and family/social out- comes, than low-severity patients did when treatment was of longer duration or higher intensity. Dual diagnosis patients with highly severe symptoms would likely benefit from a longer episode of care that includes substance abuse and psychiatric outpatient treatment. KEY WORDS: dual diagnosis; functioning outcomes; substance use outcomes; symptom severity; treatment duration and intensity. The focus on how best to treat dual diagnosis patients has grown in recent years due to increasing numbers of patients having both substance use and psychiatric disorders (Drake, Mercer-McFadden, Mueser, McHugo, & Bond, 1998; Kasprow, Rosenheck, Frisman, & DiLella, 1999). In part, Christine Timko, Ph.D., is a Research Career Scientist, and Rudolf H. Moos is a Senior Research Career Scientist, both at the Center for Health Care Evaluation, Department of Veterans Affairs Health Care System, and Stanford University Medical Center in California. This work was funded by the Department of Veterans Affairs Health Services Research and Develop- ment Service and Mental Health Strategic Health Group. The work was conducted, in part, under the auspices of the Substance Abuse Module of the VA Quality Enhancement Research Initiative. We thank Emily Wheeler for helping with the literature review and data analysis. Address for correspondence: Christine Timko, Veterans Affairs Health Care System (152-MPD), 795 Willow Road, Menlo Park, CA 94025. E-mail: ctimko@stanford.edu.  2002 Human Sciences Press, Inc. 35