Contingent incentives reduce cigarette smoking among pregnant, methadone-maintained women: results of an initial feasibility and efficacy randomized clinical trial

Abstract

Aims: This study examined the feasibility and efficacy of behavioral incentives for reducing cigarette smoking among pregnant methadone-maintained patients.

Design: Participants (n = 102) were assigned randomly to: (i) contingent behavioral incentives (CBI: n = 42); (ii) non-contingent behavioral incentives (NCBI: n = 28); or (iii) treatment as usual (TAU: n = 32).

Setting: Study procedures were implemented at the Center for Addiction and Pregnancy in Baltimore, MD.

Participants: Study participants were pregnant, methadone-maintained women enrolled in substance use disorder treatment.

Measurements: Baseline carbon monoxide (CO) levels were calculated for each participant. Subsequently, breath samples were tested three times weekly to measure changes in smoking behavior. CBI participants received incentives for target reductions from baseline: any reduction (week 1); 10% reduction (weeks 2-4), 25% reduction (weeks 5-7), 50% reduction (weeks 8-9), 75% reduction (week 10-11); and abstinence [CO < 4 parts per million (p.p.m.)] (week 12 until delivery). NCBI participants received incentives independent of smoking CO measurement results. TAU participants received no incentives, the standard treatment at the program.

Findings: CBI condition participants submitted significantly lower mean CO values than the NCBI and TAU conditions over the course of the intervention (P < 0.0001). Nearly half (48%) of the CBI participants met the 75% smoking reduction target and one-third (31%) met the abstinence target at week 12. In contrast, none of the NCBI met either the 75% or abstinence targets. Only 2% of the TAU participants met the 75% reduction and none of the TAU participants met the abstinence targets. These smoking behavior reductions did not yield significant differences in birth outcomes.

Conclusions: Cigarette smoking may be reduced significantly among pregnant, methadone-maintained women through the use of contingent reinforcement for gradual reductions in breath carbon monoxide levels.

Figure 1

Number of Patients Screened, Excluded, and Randomized to the TAU, CBI, and NCBI Study Conditions ¹Other exclusion reasons: Benzodiazepine or alcohol use (n=93); Live outside metro area (n=15); Pregnancy/medical issues (n=40); Psychiatric issues (n=38); In controlled environment (n=6); Under 18 years of age (n=1); Left treatment AMA (n=11)

Figure 2

Mean Carbon Monoxide Levels for the TAU, CBI, and NCBI Conditions by Study Week

Figure 3

CO behavioral target results across consecutive days during intervention. Within each panel, rows of data represent the CO behavioral target result for each individual participant. Dark filled squares indicate CO targets met and light filled squares indicate CO targets missed. Missing samples are denoted by empty cells. Within each panel, participants are arranged from those showing the fewest targets met on the bottom to those with the most targets met on the top.