Money matters: a meta-analytic review of the effects of financial incentives on recovery after closed-head injury

OBJECTIVE: The authors evaluated the impact of financial incentives on disability, symptoms, and objective findings after closed-head injury. METHOD: Meta-analysis was used to review the literature. Seventeen reports, covering 18 study groups and a total of 2,353 subjects, contained data from which effect sizes could be calculated. Effect sizes were aggregated after weighting for group size. After discussion, there was 100% agreement between the authors on all calculations. RESULTS: A moderate overall effect size, 0.47, was found. The effect was particularly strong for mild head trauma. The data showed more abnormality and disability in patients with financial incentives despite less severe injuries. CONCLUSIONS: Clinical evaluation of patients after closed-head injury, particularly mild head trauma, must include consideration of the effect of financial incentives on symptoms and disability.