Final answer:
The study by Higgins and colleagues found that voucher programs did not result in higher relapse rates, but instead led to increased abstinence and improved treatment outcomes.
Step-by-step explanation:
In Higgins and colleagues' study of the effectiveness of voucher programs for drug treatment and abstinence, the option that was not a finding is c) Higher relapse rates in voucher programs compared to traditional interventions. The findings highlighted an increased rate of abstinence and improved drug treatment outcomes with voucher-based interventions, as well as a positive correlation between voucher reinforcement and treatment success. These outcomes suggest vouchers can play a critical role in enhancing the treatment adherence and abstinence in programs addressing substance abuse.