Interaction effects of age and contingency management treatments in cocaine-dependent outpatients

Abstract

As the American population ages, older adults are accounting for a larger percentage of the drug-abusing population, but little attention has been given to this age group especially in regards to evaluating responsivity to different treatment modalities. Contingency management (CM) is a highly effective behavioral treatment that provides positive tangible reinforcers for objective evidence of behavior change. The purpose of this study was to examine main and interactive effects of age on outcomes in cocaine-dependent patients receiving CM with standard care (SC) or SC alone. Patients (N = 393) participating in 1 of 3 randomized trials of CM for cocaine dependence were divided into young, middle, and older age cohorts. Baseline characteristics and outcomes were compared across the age groups. The oldest age group had more medical problems than the youngest and middle age groups but had fewer legal difficulties and psychiatric symptoms. The oldest age group remained in treatment significantly longer than the other age groups, regardless of the type of treatment received. Although all age groups benefited from CM in terms of retention and longest duration of abstinence achieved, a significant age by treatment interaction effect emerged, with the older cohort improving relatively less from CM than the younger age groups. These findings demonstrate that age may play a role in moderating intervention outcomes, and tailoring CM to the needs of older and middle-aged substance abusers may be important for improving outcomes in this growing population.

Figure 1

Age distribution of patients.

Figure 2

Weeks retained in treatment based on age category and treatment condition. Values represent mean weeks and standard errors of the mean. Significant age, p = .05, and age by treatment condition effects were noted, p = .005.

Figure 3

Longest duration of abstinence achieved based on age category and treatment condition. Values represent mean weeks of documented abstinence from cocaine, opioids and alcohol and standard errors of the mean. Significant age by treatment condition effects were noted, p = .005.

Figure 4

Proportions of negative samples submitted based on age category and treatment condition. Values represent mean proportions of samples submitted that tested negative for cocaine, opioids and alcohol concurrently and standard errors of the mean. Significant age by treatment condition effects were noted, p = .005.