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.