Effect of primary medical care on addiction and medical severity in substance abuse treatment programs

J Gen Intern Med. 2003 Jan;18(1):1-8. doi: 10.1046/j.1525-1497.2003.10601.x.


Objective: To examine whether the availability of primary medical care on-site at addiction treatment programs or off-site by referral improves patients' addiction severity and medical outcomes, compared to programs that offer no primary care.

Design: Secondary analysis of a prospective cohort study of patients admitted to a purposive national sample of substance abuse treatment programs.

Setting: Substance abuse treatment programs in major U.S. metropolitan areas eligible for demonstration grant funding from the federal Substance Abuse and Mental Health Services Administration.

Respondents: Administrators at 52 substance abuse treatment programs, and 2,878 of their patients who completed treatment intake, discharge, and follow-up interviews.

Measurements: Program administrators reported whether the program had primary medical care available on-site, only off-site, or not at all. Patients responded to multiple questions regarding their addiction and medical status in intake and 12-month follow-up interviews. These items were combined into multi-item composite scores of addiction and medical severity. The addiction severity score includes items measuring alcohol and drug use, employment, illegal activities, legal supervision, family and other social support, housing, physical conditions, and psychiatric status. The medical severity score includes measures of perceived health, functional limitations, and comorbid physical conditions.

Main results: After controlling for treatment modality, geographic region, and multiple patient-level characteristics, patients who attended programs with on-site primary medical care experienced significantly less addiction severity at 12-month follow-up (regression coefficient, -25.9; 95% confidence interval [95% CI], -43.2 to -8.5), compared with patients who attended programs with no primary medical care. However, on-site care did not significantly influence medical severity at follow-up (coefficient, -0.28; 95% CI, -0.69 to 0.14). Referral to off-site primary care exerted no detectable effects on either addiction severity (coefficient, -9.0; 95% CI, -26.5 to 8.5) or medical severity (coefficient, -0.03; 95% CI, -0.37 to 0.44).

Conclusions: On-site primary medical care improves substance abuse treatment patients' addiction-related outcomes, but not necessarily their health-related outcomes. Further study is needed to discern the mechanism through which on-site primary care might improve the addiction-related outcomes of substance abuse treatment.

Publication types

  • Multicenter Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Comorbidity
  • Delivery of Health Care, Integrated*
  • Female
  • Humans
  • Male
  • Multivariate Analysis
  • Primary Health Care*
  • Regression Analysis
  • Severity of Illness Index
  • Substance Abuse Treatment Centers*
  • Substance-Related Disorders / classification
  • Substance-Related Disorders / therapy*
  • Treatment Outcome
  • United States