Incentives in the Treatment of Cocaine Dependence

Relapse rates are high in treatment samples of adults with cocaine dependence.

Cognitive behavioral therapy (CBT) is a common standard of care for cocaine dependence.

A recent clinical trial from Switzerland examined the use of financial prize incentives to augment standard CBT in the treatment of cocaine dependence.

Sixty subjects participated in this trial with the following inclusion criteria: least 18 years of age, had a DSM-IV diagnosis of cocaine dependence with at least one positive cocaine urine drug screen at baseline.

Exclusion criteria included: current psychotic disorder, current severe alcohol or benzodiazepine dependence, serious medical illness, pathological gambling, language impairment, methylphenidate use and active homelessness.

All subjects received 18 manual-based CBT sessions over 24 weeks targeted towards a goal of cocaine abstinence.

Half of the subjects received an additional treatment intervention labelled prize-based contingency management: 

• Subjects with cocaine negative urine samples (taken twice weekly in weeks 1-12 and weekly during weeks 13-24) were eligible to earn prizes
• Prizes were determined from a patient drawing from 500 chips in a bowl
• 250 chips were non-winners
• 219 had a value of $2 traded for food or hygiene rewards
• 30 had a value of $20 with a voucher for prizes in this price range
• One jumbo prize valued at $500 was present and could be traded for a television or vacation prize

Interestingly, the number of chips that was drawn started at one with the first cocaine free drug sample and increased by one with each consecutive negative sample up to a maximum of 15 chips.

Subjects relapsing after a period of abstinence returned to a one chip reward restart with the next clean urine sample.

The study failed to find a large statistically significant effect for the addition of prize-based contingency management.

However, those in the prize-based contingency management group had higher rates of clean urine samples beginning at weeks 8, 9 and 10 as well as several other later time points.

Additionally, the prize group had higher cocaine clean urine rates at 6 months follow up (66% vs 45%) although this did not reach statistical significance.

One issue with this study is the small sample size with limited power to detect clinically significant differences between treatment. The trend for improvement with adding the prize intervention suggests the potential merit of conducting a similar study using larger samples, possibly in several settings and nations.

The authors note the cost for the incentives in their design averaged $576 over the 24 week study. This additional cost is non-trivial and will need to be examined in larger samples.

Readers with more interest in this clinical trial can access the free full-text manuscript by clicking on the free full-text link in the PMID link below.

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Petitjean SA, Dürsteler-MacFarland KM, Krokar MC, Strasser J, Mueller SE, Degen B, Trombini MV, Vogel M, Walter M, Wiesbeck GA, & Farronato NS (2014). A randomized, controlled trial of combined cognitive-behavioral therapy plus prize-based contingency management for cocaine dependence. Drug and alcohol dependence, 145C, 94-100 PMID: 25456571