In a nearby town, two people had anxiety disorders in the past but not now. Three people developed anxiety disorders four or five years ago, and continue to have an anxiety disorder now. Six people developed anxiety disorders this year and continue to be so diagnosed. Which of the following might an epidemiologist write in her report concerning the rate of mental disorders in this community?

Question

Quizplus · Accepted Answer

Incidence refers to new cases occurring within a specified period (usually a year), while prevalence refers to the total number of cases at a given point or period. 
Using the information given, we can determine that the incidence of anxiety disorders this year was six (6), and the lifetime prevalence (total number of cases in the population at any point in time) is eleven (11). We can arrive at this by adding the number of people who had anxiety disorders in the past and those who currently have anxiety disorders:

- Past: 2 + 3 = 5 
- Present: 3 + 6 = 9 
- Lifetime prevalence: 5 + 9 = 11

Therefore, the best choice is B.

In a Nearby Town, Two People Had Anxiety Disorders in the Past