Anxiety disorders are one of the most common and pervasive mental disorders. The different disorders have different prevalence rates. In depth prevalence information can be found in the sections describing the DSM-IV diagnostic criteria for each disorder. One year prevalence rates refer to the percent of individuals expected to have a current diagnosis of a disorder during the preceding twelve months. Lifetime prevalence rates refer to the percent of individuals who report having been diagnosed with the disorder in their lifetime, regardless of current diagnostic status.
Estimates vary widely due to different thresholds used to calculate the presence of the disorder.
Anxiety is common throughout the lifespan. Although they are not well understood, children show a variety of fears throughout development. For example, almost all 18 month old children in the U.S. show a fear of strangers. Other fears develop throughout childhood although most disappear as the child progresses developmentally. In some cases, however, these fears can remain with the individual throughout the lifespan.