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. Author manuscript; available in PMC: 2018 Dec 1.
Published in final edited form as: Psychol Addict Behav. 2017 Jun 22;31(8):907–921. doi: 10.1037/adb0000291

Table 2.

Details of studies targeting illicit substances.

Study N Study
design		 Target of
CM		 Treatment groups Length of
CM
intervention		 Max.
possible or
avg.
earned		 Medication Verification
method		 Results Post-
intervention
follow-up		 Maternal/infant
outcomes
Chang et al. (1992) 12 Non-randomized Polydrug

  1. Fixed vouchers + enhanced substance use disorder treatment

  2. Treatment as usual

 Not reported

  1. $15/week max.

  2. NA

 Methadone Urine testing, unknown method CM > control, no statistical comparisons, but CM participants had greater abstinence and attended more prenatal visits None No statistical comparisons, but CM group had higher birth weights and gestational age
Carroll et al. (1995) 14 RCT Polydrug

  1. Fixed vouchers + enhanced substance use disorder treatment

  2. Treatment as usual

 23 weeks avg.

  1. $345 max.

  2. NA

 Methadone Urine testing, unknown methods CM = control, no differences in illicit drug use, CM participants had significantly more prenatal care visits None Not statistically significant, but trends toward higher birth weight and gestational age in CM group
Elk et al. (1995) 71 Multiple baseline across subject Cocaine

  1. Fixed vouchers with bonuses

 16 weeks avg.

  1. $816 max.

 None Urine immunoassay, TLC2, and quantification of immunoassay results Significant decrease in cocaine use, increased attendance at prenatal appointments None Not reported
Elk et al. (1998) 12 RCT Cocaine

  1. Fixed vouchers with bonuses + treatment as usual

  2. Treatment as usual

 16 weeks avg.

  1. $1184 max.

  2. NA

 None Urine immunoassay, TLC2 CM = control, nearly all subjects abstained from cocaine in both groups None Adverse perinatal outcomes significantly less common in CM group
Jones et al. (2000) 25 RCT Opioids and cocaine

  1. Fixed vouchers with bonus for 5–7 days of abstinence

  2. No vouchers

 1 week

  1. $85 max.

  2. NA

 Methadone Urine test, unknown method CM = controls None Not reported
Incentives group attended more hours of treatment than control group
Jones et al. (2001) 85 RCT Cocaine

  1. Escalating, resetting vouchers

  2. No vouchers

 1 week

  1. $3593 avg.

  2. NA

 Methadone Urine immunoassay, GCMS4 confirmation CM > controls No difference between groups at 2–4 weeks following incentives Not reported
Abstinence from opioids also higher in CM group, though not a target of CM
Silverman et al. (2001) 40 RCT Opioids and cocaine

  1. Escalating, resetting vouchers for abstinence and workplace performance

  2. Treatment as usual

 24 weeks

  1. $1013 avg.

  2. NA

 Methadone Urine immunoassay CM > control, CM participants had significantly greater abstinence from cocaine and opioids None Not reported
Jones et al. (2002) 31 Non-randomized Polydrug

  1. Fixed vouchers among compliant clients

  2. Fixed vouchers among non-compliant clients

 4 weeks

  1. $120 avg.

  2. $23 avg.

 None Urine immunoassay All participants could earn vouchers; those who attended all four opportunities to earn vouchers had significantly higher abstinence than those attending 3 or fewer visits Not statistically significant, but trend for compliant women to be abstinent at delivery Significantly higher birth weights among compliant participants, no significant difference in gestational age, birth weight ≤2500g, Apgar, hospital length of stay
Jones et al. (2004) 130 Non-randomized Polydrug

  1. Fixed vouchers + motivational interviewing + case management

  2. Fixed vouchers + motivational interviewing

  3. Drug-free controls

 4 weeks

  1. $46 avg.

  2. $37 avg.

  3. NA

 Methadone optional Urine immunoassay No overall difference between CM groups in abstinence, though significantly more women in the case management group provided one drug-free urine and two consecutive drug-free urines None Not reported
Schottenfeld et al. (2011) 145 RCT Cocaine

  1. Escalating, resetting vouchers + community reinforcement

  2. Non-contingent vouchers + community reinforcement

  3. Escalating, resetting vouchers + 12-step facilitation

  4. Non-contingent vouchers + 12-step facilitation

 24 weeks

  1. $9355 max.

  2. $935 max., yoked to group 1 earnings

  3. $935 max.

  4. $935 max., yoked to group 3 earnings

 None Urine immunoassay CM > controls, significantly greater abstinence in CM groups compared to controls, no interaction of CM with CRA or 12-step CM > controls at 3, 6 months post intervention Not reported
Tuten et al. (2012b) 133 RCT Opioids and cocaine

  1. Escalating vouchers

  2. Fixed vouchers

  3. Non-contingent vouchers

 13 weeks

  1. $296 avg.

  2. $437 avg.

  3. $220 avg.

 Methadone Urine immunoassay CM = control, no significant difference in abstinence between groups None Not reported

Note:

1

Results from 5 non-pregnant, tuberculosis patients excluded,

2

Thin layer chromatography,

3

Includes previous week when attendance was the CM target, data reported in Table 3,

4

Gas chromatography, mass spectrometry,

5

All participants also received $5 vouchers for attending counseling sessions