Tools for Assessing Generalized Anxiety Disorder
Tools for Assessing Generalized Anxiety Disorder
Generalized anxiety disorder (GAD) is a chronic, impairing and highly comorbid psychiatric condition afflicting an estimated 2.1% to 3.1% of the U.S. population during any given 12-month period (Grant et al., 2005; Kessler et al., 2005). Although historically neglected relative to other anxiety disorders, recent years have witnessed increasing attention and interest in the nature and treatment of GAD. A number of factors have contributed to these developments including elimination of GAD's status as a residual category in the DSM-III-R and several empirically based refinements in the diagnostic criteria for GAD. Among the most consequential of these revisions has been the designation of uncontrollable worry (apprehensive expectation) as the hallmark feature of the disorder and the specification of six key associated symptoms, primarily centering on motor tension (e.g., muscle tension, aches or soreness, restlessness) and vigilance (e.g., feeling keyed up or on edge, difficulty concentrating).
As currently defined in the DSM-IV-TR, a diagnosis of GAD involves excessive anxiety and worry about a number of events or activities, which occur more days than not for at least six months. The worrying is difficult to control, and the individual experiences three or more associated symptoms, including restlessness, fatigue, difficulty concentrating, irritability, muscle tension and sleep disturbance. The focus of worry is not on a situation that could be more parsimoniously subsumed under another anxiety disorder (e.g., fear of embarrassment or humiliation in social situations, as in social anxiety disorder). Additionally, there must be evidence of clinically significant functional impairment.
Given its prevalence and associated impairment, the significant burden imposed on health care resources, accurate assessment of GAD and its severity by mental health and primary care clinicians is an increasingly important goal. Reliable diagnosis and assessment of disorder severity can guide the nature, frequency and duration of therapeutic interventions. Moreover, accurate assessment of initial disorder severity provides a benchmark from which ongoing evaluation of treatment effectiveness can proceed.
Assessing Severity in GAD
Assessing the severity of GAD can be done quantitatively (e.g., a 0-10 rating scale), qualitatively (e.g., categorical classifications such as mild, moderate or severe), or with some combination of these approaches. It should apply to relevant domains (e.g., worry, associated symptoms, subjective distress, impairment in role-functioning). In the recent National Comorbidity Survey-Replication study, severity of 12-month GAD cases was evaluated among a large representative community sample (Kessler et al., 2005). Findings revealed that 32.3% of individuals with GAD were classified as serious, 44.6% of cases as moderate and 23.1% as mild, with severity defined by the consequences of GAD in several domains of functioning. Serious cases were defined by: a recent suicide attempt; substantial work limitation; substance dependence with serious role impairment; or 30 or more days out of role in the year. Moderate cases were defined by: a suicide gesture, plan or ideation; substance dependence without serious role impairment; and moderate work limitation or moderate role impairment. Disorders not meeting the criteria for serious or moderate severity were classified as mild.
A complementary way to assess the severity of GAD is to focus on the specific symptoms constituting the disorder. A number of psychometrically sound instruments designed toward this end have been reported in the anxiety disorder and GAD research literature (Table 1). (For more comprehensive reviews see Roemer and Medaglia  and Turk et al. ).
The Hamilton Anxiety Rating Scale (HAM-A) is a widely used interview measure designed to assess anxiety. Although it predates current conceptualizations of GAD, it assesses several of the associated symptoms of GAD. The HAM-A features both psychic and somatic anxiety subscales. The psychic subscale, which is comprised of items that address the more subjective cognitive and affective components of anxious experience (e.g., anxious mood, tension, fears, difficulty concentrating), is particularly useful in assessing the severity of GAD. In contrast, the somatic subscale emphasizes features of GAD that are somewhat less typical, including autonomic arousal, respiratory and cardiovascular symptoms. The HAM-A has become an industry standard in clinical trials of pharmacotherapy and psychotherapy for GAD. Full-scale pretreatment scores of 18 to 20 or greater are a common index of severity required for entry into a clinical trial. A 40% to 50% reduction in the HAM-A total score (i.e., a full-scale score in the range of 8 to10 or less) is a typical criterion for defining treatment response (Gelenberg et al., 2000; Rickels et al., 2005). One notable limitation in using the HAM-A to assess GAD severity is that it does not evaluate excessive or difficult-to-control worry, which is recognized as the central feature of GAD in current conceptualizations (e.g., DSM-IV-TR).
Recently, Shear and colleagues (in press) have developed the Generalized Anxiety Disorder Severity Scale (GADSS). The GADSS was explicitly designed to be a specific measure of GAD severity, and it facilitates probing of typical domains of worry (e.g., future, health, finances, relationships) and detection of the six associated symptoms defining GAD. Severity is assessed by ratings of frequency and distress due to worrying, the associated symptoms of GAD, and impairment/interference in social and work functioning. Preliminary evaluation has shown that the GADSS has good reliability, validity and treatment sensitivity.