Do incentives undermine intrinsic motivation? Increases in intrinsic motivation within an incentive-based intervention for people living with HIV in Tanzania

Background Cash and in-kind incentives can improve health outcomes in various settings; however, there is concern that incentives may 'crowd out' intrinsic motivation to engage in beneficial behaviors. We examined this hypothesis in a randomized trial of food and cash incentives for people living with HIV infection in Tanzania. Methods We analyzed data from 469 individuals randomized to one of three study arms: standard of care, short-term cash transfers, or short-term food assistance. Eligible participants were: 1) >= 18 years old; 2) HIV-infected; 3) food insecure; and 4) initiated antiretroviral therapy (ART) <= 90 days before the study. Food or cash transfers, valued at similar to$11 per month and conditional on attending clinic visits, were provided for <= 6 months. Intrinsic motivation was measured at baseline, 6, and 12 months using the autonomous motivation section of the Treatment Self-Regulation Questionnaire (TSRQ). We compared the change in TSRQ score from baseline to 6 and 12 months and the change within study arms. Results The mean intrinsic motivation score was 2.79 at baseline (range: 1-3), 2.91 at 6 months (range: 1-3), and 2.95 at 12 months (range: 2-3), which was 6 months after the incentives had ended. Among all patients, the intrinsic motivation score increased by 0.13 points at 6 months (95% CI (0.09, 0.17), Cohen's d = 0.29) and 0.19 points at 12 months (95% CI (0.14, 0.24), Cohen's d = 0.49). Intrinsic motivation also increased within each study group at 6 months: 0.15 points in the food arm (95% CI (0.09, 0.21), Cohen's d = 0.37), 0.11 points in the cash arm (95% CI (0.05, 0.18), Cohen's d = 0.25), and 0.08 points in the comparison arm (95% CI (-0.03, 0.19), Cohen's d = 0.21); findings were similar at 12 months. Increases in motivation were statistically similar between arms at 6 and 12 months. Conclusion Intrinsic motivation for ART adherence increased significantly both overall and within the food and cash incentive arms, even after the incentive period was over. Increases in motivation did not differ by study group. These results suggest that incentive interventions for treatment adherence should not be withheld due to concerns of crowding out intrinsic motivation.