Prevalence

Prevalence is the share of a population that has a condition at a given time. It answers the question "how many people have this."

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.

Prevalence is usually written as a percentage. It can cover different windows of time. Point prevalence is how many people have the condition on a single day. Past-year prevalence is how many had it at any time in the last twelve months. Lifetime prevalence is how many have ever had it. The window changes the number, so the window matters.

Almost every headline anxiety statistic is a prevalence figure. When you read that about 19 percent of US adults had an anxiety disorder in the past year, that's past-year prevalence. When you read 31 percent at some point in life, that's lifetime prevalence. Confusing the two is one of the most common errors in reading anxiety data.

A survey of 30,000 adults finds that 5,700 of them met criteria for an anxiety disorder in the past year. The past-year prevalence is 19 percent.

Always check the window and the method. A prevalence number from a survey that uses a full diagnostic interview will differ from one that uses a short symptom screener. Higher isn't the same as more accurate. Symptom screeners tend to report higher numbers than diagnostic interviews.