Definition	Generalized anxiety disorder (GAD) is defined as excessive worry and tension about everyday events and problems, on most days, for at least six months to the point where the person experiences distress or has marked difficulty in performing day-to-day tasks.¹ It may be characterized by the following symptoms and signs: increased motor tension (fatigability, trembling, restlessness, and muscle tension); autonomic hyperactivity (shortness of breath, rapid heart rate, dry mouth, cold hands, and dizziness); and increased vigilance and scanning (feeling keyed up, increased startling, and impaired concentration), but not panic attacks.¹ One non-systematic review of epidemiologic and clinical studies found marked reduction of quality of life and psychosocial functioning in people with anxiety disorders (including GAD).² It also found that (using the Composite Diagnostic International Instrument) people with GAD have low overall life satisfaction and some impairment in ability to fulfill roles, social tasks, or both.²
Incidence/Prevalence	Assessment of the incidence and prevalence of GAD is difficult, because a large proportion of people with GAD have a comorbid diagnosis. One nonsystematic review identified the U.S. National Comorbidity Survey, which found that more than 90 percent of people diagnosed with GAD had a comorbid diagnosis, including dysthymia (22 percent), depression (39 to 69 percent), somatization, other anxiety disorders, bipolar disorder, or substance abuse.³ The reliability of the measures used to diagnose GAD in epidemiologic studies is unsatisfactory.^4,5 One U.S. study, with explicit diagnostic criteria (DSM-III-R), estimated that 5 percent of people will develop GAD at some time during their lives.⁵ A recent cohort study of people with depressive and anxiety disorders found that 49 percent of people initially diagnosed with GAD retained this diagnosis after two years.⁶ One nonsystematic review found that the incidence of GAD in men is only one half the incidence in women.⁷ One nonsystematic review of seven epidemiologic studies found reduced prevalence of anxiety disorders in older people.⁸ Another nonsystematic review of 20 observational studies in younger and older adults suggested that the autonomic arousal to stressful tasks is decreased in older people, and that older people become accustomed to stressful tasks more quickly than younger people.⁹
Etiology/Risk Factors	One community study and a clinical study have found that GAD is associated with an increase in the number of minor stressors, independent of demographic factors,¹⁰ but this finding was common in people with other diagnoses in the clinical population.⁶ One non-systematic review (five case control studies) of psychologic sequelae to civilian trauma found that rates of GAD reported in four of the five studies were increased significantly compared with a control population (rate ratio: 3.3; 95 percent confidence interval [CI]: 2.0 to 5.5).¹¹ One systematic review of cross-sectional studies found that bullying (or peer victimization) was associated with a significant increase in the incidence of GAD (effect size: 0.21).¹² One systematic review (search date not stated) of the genetic epidemiology of anxiety disorders(including GAD) identified two family studies and three twin studies.¹³ The family studies (45 index cases; 225 first-degree relatives) found a significant association between GAD in the index cases and in their first-degree relatives (odds ratio [OR]: 6.1; 95 percent CI: 2.5 to 14.9). The twin studies (13,305 people) estimated that 31.6 percent (95 percent CI: 24 to 39 percent) of the variance to liability to GAD was explained by genetic factors.¹³
Prognosis	GAD often begins before or during young adulthood and can be a lifelong problem.¹⁴ Spontaneous remission is rare.
Clinical Aims	To reduce anxiety; to minimize disruption of day-to-day functioning; and to improve quality of life, with minimum adverse effects.
Clinical Outcomes	Severity of symptoms and effects on quality of life, as measured by symptom scores: usually the Hamilton Anxiety Scale (HAM-A), State-Trait Anxiety Inventory, or Clinical Global Impression Symptom Scores. Where numbers needed to treat are given, these represent the number of people requiring treatment within a given time period (usually six to 12 weeks) for one additional person to achieve a certain improvement in symptom score. The method for obtaining numbers needed to treat was not standardized across studies. Some used a reduction by, for example, 20 points in the HAM-A as a response, others defined a response as a reduction, for example, by 50 percent of the premorbid score. We have not attempted to standardize methods, but instead have used the response rates reported in each study to calculate numbers needed to treat. Similarly, we have calculated numbers needed to harm from original trial data.