Incidence

Incidence is the rate at which new cases of a condition appear in a population over a period of time. It counts only the new cases.

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.

Incidence and prevalence are easy to mix up. Prevalence counts everyone who has the condition. Incidence counts only the people who developed it during a set window, usually a year. Incidence describes how fast a condition is appearing. Prevalence describes how much of it is present overall.

Incidence is harder to measure for anxiety than prevalence, because it means following people over time and catching the moment a disorder begins. Most anxiety statistics you see are prevalence. When a report says anxiety is rising, check whether it means more new cases each year, which is incidence, or simply more people carrying the condition, which is prevalence.

In a town of 100,000 adults, 800 develop an anxiety disorder for the first time during one year. The incidence is 0.8 percent per year.

A condition can have steady incidence but rising prevalence if people stay ill longer or recover more slowly. So a rising prevalence doesn't always mean a condition is striking more people. Read carefully which measure a report uses.