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See also:
Summary of Sampling Design

Data Collection
Treatment Modalities Represented


The Drug Abuse Treatment Outcome Studies (DATOS) project was a collaborative national research program for evaluating the effectiveness of community-based drug treatment in the United States. The National Development and Research Institute (NDRI) served as the Coordinating Center as well as one of the four DATOS Research Centers. The other three centers are located at the Institute of Behavioral Research at Texas Christian University (TCU), the Drug Abuse Research Center at the University of California at Los Angeles (UCLA), and the Services Research Branch of the National Institute on Drug Abuse (NIDA). As Coordinating Center, NDRI was responsible for maintaining databases and documentation of DATOS studies as well as for overseeing data collection for future follow-ups. Each Research Center organized its studies around a central theme; NDRI focused on treatment selection, access, and utilization, TCU examined treatment engagement and retention, UCLA addressed addiction and treatment careers, and NIDA specialized in applications and policy development.

Results from a series of core studies published in the Psychology of Addictive Behaviors (Simpson & Curry, eds., 1997), Archives of General Psychiatry (Simpson et al, 1999), and Drug and Alcohol Dependence (Simpson & Brown, eds., 1999) describe some of the highlights and major findings from this project.


Summary of Sampling Design 

DATOS: Overview of Sampling Plan

A total of 96 treatment programs in 11 large U.S. cities were chosen to reflect typical community-based treatment services available to the public (see Overview of Sampling Plan). Geographic location and type of program as well as the type of clients they served were considered in designing the sampling plan. Participating programs were located in Chicago, Houston, Miami, Minneapolis, Newark, New Orleans, New York, Phoenix, Pittsburgh, Portland, and San Jose. The overall methodology used to compile the database used in DATOS studies, including client samples and program characteristics, used to meet research objectives is described by Flynn, Craddock, Hubbard, Anderson, and Etheridge (1997).

  • Intake Sample: A total of 10,010 clients entered the 96 treatment programs that participated in DATOS during 1991-1993. Overall, this treatment sample was 66% male; 47% African American; and 13% Hispanic, with a mean age of 33 years. However, these and other client characteristics varied across modalities, reflecting their different therapeutic and operational characteristics.
  • Follow-up Sample: 4,229 of the eligible clients who completed the two-stage intake interviews were selected for follow-up (using a stratified random design). Altogether, 74% (n=3,147) were located, including 70% (n=2,966) who were successfully interviewed, 1.5% (n=64) who were deceased, and 2.7% (n=117) who refused to participate. Gender, ethnicity, and average age were not significantly different between the intake and follow-up samples.


Data Collection

Repeated measures methodology was used, combining detailed levels of measurement and multiple comparison groups. Data collection forms included sets of standardized instruments recommended by clinical experts, and many of the measures used were adapted from earlier large-scale follow-up studies.

  • Intake 1 and Intake 2 were conducted by trained  interviewers (approximately 1 week apart) and addressed the following information domains.
  • Demographic characteristics
  • Employment status, work history, and income
  • Criminal justice status
  • Living situation, and child custody status
  • Mental health, and psychiatric diagnosis
  • Medical and health-related data
  • Level of drug and alcohol use before treatment
  • Primary drug use and patterns of dependence
  • HIV risk behaviors
  • During-Treatment Interviews were completed at 1 month after admission, and again at 3 and 6 months. Questions were included about service delivery and client satisfaction.
  • Follow-up Interviews were administered at 12-months after treatment termination (although for long-term methadone clients treated for more than 12 months in DATOS, the follow-up interview had to be scheduled at 24 months after admission). It replicated much of the Intake and focused on key behaviors during the year before the follow-up interview. (An additional follow-up is planned for approximately 48 months posttreatment.)
  • Treatment Process Questionnaires were sent to counselors and program directors at 75 selected programs approximately 8 months after during-treatment data were collected. Questions were asked about program and treatment structure, philosophy, available services, policy, staffing, treatment planning, and aftercare. Program directors were asked about program organization and financing. Overall, 71 questionnaires (95%) were completed.



  • Specially trained and supervised interviewers were hired to carry out Intake and During-Treatment data collection in order to assure that programs were not inconvenienced by the research. Trained professional survey interviewers conducted follow-up surveys in the community. Quality control procedures were in place for each step of data management, data editing and entry, and document control.
  • Clients were compensated $10 for each Intake and During-Treatment interview, and $15 for a Follow-up interview.


Treatment Modalities Represented

  • Outpatient Methadone Treatment (OMT) programs administered the medication methadone to reduce cravings for heroin, in addition to providing counseling and case management services. Some provided long-term methadone maintenance for clients and others used methadone to taper to abstinence, but all programs had expected stays of 2 years or longer. Private for-profit methadone clinics, nonprofit community-based programs, hospital-based outpatient clinics, and county-managed programs were represented. There were 29 OMT programs with 1,540 clients in the DATOS sample.
  • Long-Term Residential (LTR) programs offered drug-free treatment in a residential setting, with planned stays ranging from 4 months to 2 years. LTR programs in DATOS included traditional therapeutic communities, modified therapeutic communities, and other programs requiring in-residence treatment; most expected clients to stay at least 9 months. There were 21 LTR programs with 2,774 clients in the DATOS sample.
  • Outpatient Drug-Free (ODF) programs are characterized by a wide range of therapeutic approaches such as cognitive-behavioral, insight-oriented, supportive, and 12-step. All planned for clients to stay in treatment for at least 3 months, and most expected 6 months or longer. Therapeutic community managed outpatient programs, nonprofit community programs, mental health and short-term managed programs, and private for-profit programs were included. There were 32 ODF programs with 2,574 clients in the DATOS sample.
  • Short-Term Inpatient (STI) programs generally kept clients in-residence for up to 30 days, with a focus on medical stabilization, abstinence, and lifestyle changes. They included free-standing nonprofit and for-profit short-term programs, public and nonprofit hospital programs, and county-managed programs. Due to changes in insurance coverage and a national trend toward "managed care" during the time this project was being conducted, however, planned duration of treatment became shorter over time. Most of the STI programs studied have now closed or been converted to other types of facilities. There were STI 14 programs with 3,122 clients in the DATOS sample.



Simpson, D. D., & Curry, S. J. (Eds.) (1997). Special Issue: Drug Abuse Treatment Outcome Study (DATOS). Psychology of Addictive Behaviors, 11(4).

Simpson, D. D., Joe, G. W., Fletcher, B. W., Hubbard, R. L., & Anglin, M. D. (1999).  A national evaluation of treatment outcomes for cocaine dependence.  Archives of General Psychiatry, 56, 507-514.    [Abstract]

Simpson, D. D. & Brown, B. (Eds.,) (1999). Special issue:  Treatment process and outcome studies from DATOS.  Drug and Alcohol Dependence, 57(2).  [Summary]

Flynn, P. M., Craddock, S. G., Hubbard, R. L., Anderson, J., & Etheridge, R. M. (1997). Methodological overview and research design for the Drug Abuse Treatment Outcome Study (DATOS). Psychology of Addictive Behaviors, 11(4), 230-243. [Abstract]

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July 14 2006

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