Abstract
AIMS: To test if contingency management (CM) interventions for alcohol and drug abstinence were associated with increased alcohol and drug abstinence among American Indian adults with alcohol dependence who also use drugs. DESIGN: In this 2 × 2 factorial randomized controlled trial, American Indian adults with alcohol dependence who also used drugs were randomized to four conditions: (1) incentives for submission of urine samples only (control condition), (2) CM incentives for alcohol abstinence, (3) CM incentives for drug abstinence or (4) CM incentives for abstinence from both alcohol and drugs. SETTING: A Northern Plains Reservation in the United States. PARTICIPANTS: A total of 114 American Indian adults aged 35.8 years (standard deviation = 10.4); 49.1% were male. INTERVENTION AND COMPARATOR: Participants received incentives if they demonstrated abstinence from alcohol (CM for alcohol, n = 30), abstinence from their most frequently used drug (CM for drugs, n = 27) or abstinence from both alcohol and their most frequently used drug (CM for alcohol and drugs, n = 32) as assessed by urine tests. Controls (n = 25) received incentives for submitting urine samples only. MEASUREMENTS: Primary outcomes were urine ethyl glucuronide (alcohol) and drug tests conducted three times per week during the 12-week intervention period. Data analyses included listwise deletion and multiple imputation to account for missing data. FINDINGS: The three CM groups were significantly (P < 0.05) more likely to submit alcohol-abstinent urine samples compared with the control condition, with odds ratios ranging from 2.4 to 4.8. The CM for drugs (OR = 3.2) and CM for alcohol and drugs (OR = 2.5) were significantly more likely to submit urine samples that indicated drug abstinence, relative to the control condition (P < 0.05). However, these differences were not significant in multiple imputation analyses (P > 0.05). CONCLUSIONS: Contingency management (CM) incentives for abstinence were associated with increased alcohol abstinence in American Indian adults diagnosed with alcohol dependence who also used drugs, living on a rural reservation. The effect of CM incentives on drug abstinence was inconclusive.