Impact of program services on treatment outcomes of patients with comorbid mental and substance use disorders.

General population surveys and clinical studies have demonstrated that a majority of individuals with drug abuse problems have a co-occurring mental disorder (1-3). Individuals with co-occurring mental and substance use disorders have higher rates of treatment use compared with individuals with only one disorder (4-6), although most individuals with co-occurring disorders do not receive adequate treatment for either or both disorders (7-9). National survey data show that over half of adults with co-occurring disorders received neither substance abuse nor mental health treatment in the past year (10). Several studies have demonstrated that patients with serious mental disorders are prevalent within substance abuse treatment programs (ranging from about one-fifth to one-half) (11-13). Yet access to mental health services among individuals in substance abuse treatment is often problematic because of persistent administrative, funding, and structural barriers (14,15). However, there is increasing recognition of the need to provide integrated treatment that combines mental health and substance abuse treatment in one setting with a unified treatment plan (16-18). A growing body of literature has examined the treatment outcomes of individuals with co-occurring disorders in substance abuse treatment programs. In general, research has shown that these individuals have lower rates of completing treatment, shorter stays in treatment, and higher rates of relapse and rehospitalization after treatment (19-25). Longer stays in residential treatment and participation in aftercare services, including outpatient mental health treatment, have been associated with better posttreatment functioning among individuals with co-occurring disorders for up to five years after treatment (26-33). A critical component of service delivery to individuals with co-occurring disorders in substance abuse treatment is the provision of mental health care and other comprehensive services. An accumulating body of evidence shows that individuals who receive a greater number of comprehensive services while in treatment, particularly if the treatment is targeted to their specific needs, show improved outcomes (34-37). Yet regional (38), state-level (39), and national (40) surveys of treatment providers have shown that most drug treatment programs do not provide specialized services for patients with co-occurring disorders. Moreover, there has been little change in the availability of these services in publicly funded programs in the past decade (41,42), and privately funded substance abuse treatment programs are increasingly referring patients who have co-occurring mental disorders to external providers, rather than providing these services on site (43). This article reports on a study of treatment outcomes of individuals with co-occurring disorders who received residential drug treatment from programs that varied as to whether they provided services specifically for individuals with co-occurring disorders. We examined the independent effects of preexisting patient characteristics, relevant program characteristics, and services received on treatment outcomes six months after patients were admitted for treatment. We hypothesized that patients who were treated in programs that provided more specialized services for individuals with co-occurring disorders would have higher rates of service use and better posttreatment outcomes, compared with those treated in other programs.