Number needed to treat (NNT)

The number needed to treat, or NNT, is how many people would need to receive a treatment for one extra person to benefit.

This term is specific to research interpretation and is defined on AnxietyResearch. Shrinktionary, the network's language layer, doesn't currently carry a canonical entry for it.

NNT turns a trial result into a practical number. If a treatment has an NNT of 5, then on average 5 people need to take it for 1 more person to improve than would have improved anyway. A lower NNT means a more effective treatment. The best possible NNT is 1, where everyone treated benefits.

NNT is one of the most useful ways to understand what a trial result means in real life. It's more concrete than an effect size or a p-value. It also makes clear that no treatment helps everyone. Even a good treatment has an NNT above 1.

An anxiety medication has an NNT of 6 for a meaningful response. For every 6 people who take it, about 1 more responds than would have on placebo.

NNT depends on the comparison, the outcome chosen, and the length of the study, so the same treatment can have different NNTs in different trials. It's most useful read next to the number needed to harm, which counts how many people are harmed by side effects.