حد آستانه تشخیصی اختلال اضطراب فراگیر در جامعه: چشم انداز تکاملی

Discussion surrounds the question as to whether criteria for generalized anxiety disorder (GAD) should change, particularly in youth. This study examines the effects of possible criteria changes on GAD prevalence and clinical correlates. DSM-IV GAD was assessed using the M-CIDI in a community sample of adolescents and young adults. Diagnostic thresholds were modified in two age spans (9–20 and 21–34 years) using a person-by-year data file (N = 38,534 cases). Relaxing the duration or excessiveness criteria led to the most pronounced changes in GAD prevalence, while relaxing frequency, uncontrollability, or associated-symptom criteria had smaller effects. A lower duration requirement increased rates more in older than younger age spans. Opposite effects occurred for changes in associated-symptoms or clinical-significance criteria. Broader GAD definitions identified cases in both age spans that appeared mostly milder than DSM-IV cases but that still differed from non-GAD cases in various clinical factors and validators. Developmental aspects require stronger consideration in future diagnostic systems.

The diagnosis of generalized anxiety disorder (GAD) has been surrounded by controversy. Diagnostic criteria have evolved with each DSM revision, based on efforts to distinguish GAD from normal stress reactions and other disorders as well as to improve reliability (Brown et al., 1994 and Brown et al., 2001). DSM-III (APA, 1980) defined GAD as “generalized, persistent anxiety of at least 1 month duration” accompanied by an unspecified number of various other symptoms. In DSM-III-R (APA, 1987) “unrealistic and excessive anxiety and worry (apprehensive expectation) about two or more life circumstances” was defined as the core feature of the disorder. The required duration was increased to 6 months, and the number of associated symptoms was specified (six out of 18 from motor tension, autonomic and/or vigilance clusters). DSM-IV (APA, 1994) made further changes by requiring anxiety and worry (apprehensive expectation) about a number of events or activities to be “excessive” and “difficult to control”. Autonomic symptoms were deleted from the criteria leaving six hypervigilance/tension symptoms of which at least three were required for diagnosis (one for youth). As for other disorders in DSM-IV, the GAD diagnosis required clinical significance as demonstrated by impairment or distress. Recent epidemiological research suggests that the DSM-IV GAD definition may fail to identify a number of patients with clinically significant anxiety and worry. This suggestion is based on analyses varying the threshold for GAD ‘caseness’ as defined by the DSM diagnostic criteria. In individuals with high levels of anxiety and worry, failure to meet the 6-month duration criterion is the most frequent reason for not reaching the DSM-IV diagnostic threshold (Carter et al., 2001, Hoyer et al., 2002 and Ruscio et al., 2007). Compared to individuals with six-month duration of symptoms, those with shorter duration are similar in terms of many clinical features such as associated symptoms, age-of-onset, or impairment (Bienvenu et al., 1998, Kessler et al., 2005b, Lee et al., 2009 and Wittchen et al., 2002b). This is relevant given findings that unreliability in the determination of the duration criterion largely compromises overall retest-reliability for GAD (Wittchen et al., 1998a). The ‘excessiveness’ criterion is controversial due to imprecision in the definition (Ruscio et al., 2005), which also seems to contribute to diminished reliability (Wittchen et al., 1995). However, the excessiveness criterion identifies a unique group of patients in terms of age-of-onset, persistence, and comorbidity (Ruscio et al., 2005). There is little data on the ‘uncontrollability’ criterion (Andrews et al., 2010). Some research has shown specificity of this criterion in GAD (Hoyer et al., 2002 and Hoyer et al., 2001) with some indication for a GAD gradient as evidenced by fairly high rates of uncontrollability in high trait worriers or subthreshold GAD cases (Hoyer et al., 2002 and Ruscio, 2002). While retaining the associated hypervigilance/tension symptoms from DSM-III-R in DSM-IV had some empirical support (Marten et al., 1993), the range and required number of associated symptoms had not been evaluated systematically. Recent research suggests that GAD is usually associated with more than just three out of the six DSM-IV symptoms (Beesdo, 2006, Brown et al., 1995 and Carter et al., 2001). In preparation for DSM-5, GAD criteria are in need of scrutiny. As part of such an examination, it might be particularly helpful to compare characteristics among individuals meeting the current DSM-IV GAD definition, relative to other definitions, in terms of various clinical factors. Indications for a GAD continuum (e.g. Ruscio et al., 2001) justify the search for different diagnostic thresholds by considering the impact of different criteria on prevalence and key correlates (Ruscio, 2009). Consideration of a range of ‘validators’ has been promoted (Regier et al., 2009). It is particularly important to perform such examinations in youth given that DSM-IV applies different definitions of GAD in youth and adults. This difference reflects the fact that DSM-III-R had labeled youth with persistent worries or concerns and associated symptoms as suffering from Overanxious Disorder (OAD). In clinical samples, excellent overlap between DSM-III-R OAD and DSM-IV GAD was found (Kendall and Warman, 1996 and Tracey et al., 1997). Moreover, evidence supported the decision in DSM-IV to use lower symptom thresholds for youth relative to adult GAD (Tracey et al., 1997). Nevertheless, epidemiologic data raise questions about applications of DSM-IV GAD definition for youth based on findings on prevalence (lower for GAD than OAD), onset (later for GAD than OAD), and longitudinal course (lack of associations between OAD and later GAD) (Beesdo et al., 2009, Beesdo et al., 2010, Bittner et al., 2007, Cohen et al., 1993, Kessler et al., 2005a, Pine et al., 1998 and Velez et al., 1989). Specifically, it remains unclear the degree to which changes to the current DSM-IV GAD definition would uniquely affect diagnosis among youth and adults. The current study addresses these issues in a prospective-longitudinal community study among adolescents and young adults.