Kc. Kirby et al., SCHEDULE OF VOUCHER DELIVERY INFLUENCES INITIATION OF COCAINE ABSTINENCE, Journal of consulting and clinical psychology, 66(5), 1998, pp. 761-767
This study examined whether voucher delivery arrangements affect treat
ment outcome. First, 90 cocaine-dependent adults were randomly assigne
d to behavioral counseling or counseling plus vouchers for cocaine-fre
e urine samples. The value of each voucher was low at the beginning bu
t increased as the patient progressed (Voucher Schedule 1). Voucher Sc
hedule 1 produced no improvements relative to counseling only. Next, 2
3 patients received vouchers on either Voucher Schedule 1 or Voucher S
chedule 2. Voucher Schedule 2 began with high voucher values, but requ
irements for earning vouchers increased as the patient progressed. Ave
rage durations of cocaine abstinence were 6.9 weeks on Voucher Schedul
e 2 versus 2.0 weeks on Voucher Schedule 1 (p =.02). This confirms tha
t vouchers can assist in initiating abstinence and that voucher delive
ry arrangements are critical.