number needed to harm (NNH)

Introduction

1/absolute risk increase.

For example, if risk with treatment is 20% vs 5% for placebo, the absolute risk increase is 0.20-0.05 = 0.15.

Thus, the number need to harm is 1/0.15 = 6.667 ~ 7

The number of patients needed to treat for a single patient to be harmed.

More general terms

• statistics (biostatistics)

Additional terms

• relative risk reduction (RRR)