Prevalence and Incidence Studies of Anxiety Disorders: A Systematic Review of the Literature

Article excerpt

Objective: To present the results of a systematic review of literature published between 1980 and 2004 reporting findings of the prevalence and incidence of anxiety disorders in the general population.

Method: A literature search of epidemiologic studies of anxiety disorders was conducted, using Medline and HealthSTAR databases, canvassing English-language publications. Eligible publications were restricted to studies that examined age ranges covering the adult population. A set of predetermined inclusion and exclusion criteria were used to identify relevant studies. Prevalence and incidence data were extracted and analyzed for heterogeneity.

Results: A total of 41 prevalence and 5 incidence studies met eligibility criteria. We found heterogeneity across 1-year and lifetime prevalence rates of all anxiety disorder categories. Pooled 1-year and lifetime prevalence rates for total anxiety disorders were 10.6% and 16.6%. Pooled rates for individual disorders varied widely. Women had generally higher prevalence rates across all anxiety disorder categories, compared with men, but the magnitude of this difference varied.

Conclusion: The international prevalence of anxiety disorders varies greatly between published epidemiologic reports. The variability associated with all anxiety disorders is considerably smaller than the variability associated with individual disorders. Women report higher rates of anxiety disorders than men. Several factors were found to be associated with heterogeneity among rates, including diagnostic criteria, diagnostic instrument, sample size, country studied, and response rate.

(Can J Psychiatry 2006;51:100-113)

Clinical Implications

* Significant heterogeneity in the prevalence of anxiety disorders signals the need for population-specific health policies and planning.

* The prevalence of anxiety disorders eclipses the capacity of specialized mental health services.

* Anxiety disorders remain prevalent throughout ages 18 to 64 years.

Limitations

* The observed heterogeneity may be related to environmental or cultural factors associated with the location of each contributing investigation.

* Variance owing to methods of diagnosis and measurement account for a limited portion of the observed heterogeneity.

* An insufficient number of incidence studies are available to clarify details concerning the onset of symptoms.

Key Words: anxiety disorders, panic disorder, phobia, obsessive-compulsive disorder, posttraumatic stress disorder, generalized anxiety disorder, prevalence, incidence, systematic review

In recent years, it has been increasingly acknowledged not only that anxiety disorders are highly prevalent, but also that the burden of illness associated with these disorders is often considerable. A broad understanding of the etiology of anxiety includes a multiplicity of factors, such as biological, psychological, and social determinants, which are mediated by a range of risk and protective factors. Cross-cultural studies in epidemiology are a critical source of information regarding the interplay between these factors. Effective forms of intervention are available and are the subject of ongoing research, but it is an immense public health challenge to coordinate the delivery of these programs and services. Studies in comparative epidemiology play a vital role in the development of health policy concerning anxiety. Empirical knowledge of regional prevalence is fundamental to understanding the relative demand for services. Such knowledge is also necessary to identify the most appropriate avenues for intervention.

The present review, which is the fifth in a series of papers that will present systematic reviews of the prevalence and incidence of psychiatric disorders drawn from studies published in the English literature in the years 1980 to 2004, sought to synthesize international research on this topic. …