Objective: The study examined the association between fidelity of programs to the assertive community treatment model and client outcomes in dual disorders programs. Methods: Assertive community treatment programs in the New Hampshire dual disorders study were classified as low-fidelity programs (three programs) or high-fidelity programs (four programs) based on extensive longitudinal process data. The study included 87 clients with a dual diagnosis of severe mental illness and a comorbid substance use disorder. Sixty-one clients were in the high-fidelity programs, and 26 were in the low-fidelity programs. Client outcomes were examined in the domains of substance abuse, housing, psychiatric symptoms, functional status, and quality of life, based on interviews conducted every six months for three years. Results: Clients in the high-fidelity assertive community treatment programs showed greater reductions in alcohol and drug use and attained higher rates of remission from substance use disorders than clients in the low-fidelity programs. Clients in high-fidelity programs had higher rates of retention in treatment and fewer hospital admissions than those in low-fidelity programs. No differences between groups were found in length of hospital stays and other residential measures, psychiatric symptoms, family and social relations, satisfaction with services, and overall life satisfaction. Conclusions: Faithful implementation of, and adherence to, the assertive community treatment model for persons with dual disorders was associated with superior outcomes in the substance use domain. The findings underscore the value of measures of model fidelity, and they suggest that local modifications of the assertive community treatment model or failure to comply with it may jeopardize program success.
