The objective of this paper is to provide a review on available data to date on the epidemiology of GAD in Europe, and to highlight areas for future research. MEDLINE searches were performed and supplemented by consultations with experts across Europe to identify non-published reports. Despite variations in the design of studies, available data suggest that (a) about 2% of the adult population in the community is affected (12-month prevalence), (b) GAD is one of the most frequent (up to 10%) of all mental disorders seen in primary care, (c) GAD is a highly impairing condition often comorbid with other mental disorders, (d) GAD patients are high utilizers of healthcare resources, and (e) despite the high prevalence of GAD in primary care, its recognition in general practice is relatively low. Marked data deficits are: lack of data from eastern European countries, lack of information about the natural course of GAD in unselected samples, the vulnerability and risk factors involved in the aetiology of GAD and lack of data about adequate and inappropriate treatments in GAD patients as well as the associated and societal costs of GAD.
Generalized Anxiety Disorder (GAD) is usually described as a “severe” and “chronic” anxiety disorder, which is treatable. Prior to 1980, when the diagnosis of GAD was first conceptualized in the DSM-III (APA, 1980), patients with GAD-like symptomatology were usually grouped along with patients with panic disorder-like manifestations under the diagnostic term “anxiety neurosis” — a diagnosis that is still more familiar to many clinicians than GAD in Europe. Since the inclusion of GAD in DSM-III, this diagnosis has received considerable fundamental and clinical research interest (see e.g. Heimberg et al., 2004) and has also been studied in various epidemiological investigations in Europe. Furthermore, several psychological and pharmacological treatments for GAD have been developed and tested in clinical trials (see for review Huppert and Sanderson, 2002 and Sussman and Stein, 2002) and a number of drugs have been approved for treatment of GAD (Ballenger et al., 2001).
Research progress, however, has been somewhat impeded by the changing diagnostic criteria for GAD over the past several decades. Specifically, diagnostic criteria of GAD have been changed substantially since 1980 in the subsequent DSM revisions, and even the current DSM-IV and the ICD-10 criteria for GAD differ considerably. These differences have had profound impact on findings from epidemiological studies, as will be discussed below. Changes to the content of the diagnostic criteria have occurred in the majority of domains, including: (i) the duration criterion for core symptoms have shifted from an initial 1-month (DSM-III, 1980) to a stricter 6-month criterion in DSM-III-R and DSM-IV (APA, 1994), (ii) the definition of anxious worrying as a core criterion is increasingly strict, and (iii) the type and number of associated GAD symptoms was considerably revised in DSM-IV (i.e., instead of a long list of predominant anxiety symptoms, there are now only a few symptoms mostly describing symptoms of hypervigilance, hyperarousal, and tension; symptoms reflecting autonomic hyperactivity were deleted). It should be noted, however, that this change was not made in the ICD-10, which continues to use a much broader spectrum of symptoms. The diagnostic hierarchy exclusion criteria used in DSM offer another source of potential confusion. These rules require that, when another Axis I disorder is present, the diagnosis of GAD should be made only when the focus of the anxiety is unrelated to the other disorder. In addition, GAD symptoms may not be due to the direct physiological affects of a substance or general medical condition, and they do not occur exclusively during a mood disorder, a psychotic disorder, or a pervasive developmental disorder.
Currently, the most widely used diagnostic criteria for GAD in clinical and research settings are DSM-IV. DSM-IV requires excessive and uncontrollable anxieties, worries, or tension about a number of everyday events; the anxious worrying must be associated with at least 3 vigilance or motoric symptoms and the symptoms must cause clinically significant distress or impairment in important areas of daily functioning. In addition, the DSM-IV exclusion criteria apply (see above). It should be noted that DSM-IV allows the GAD-diagnosis also to be made in children, requiring however only one – instead of three as required for adults – of the additional associated symptoms. In DSM-III and DSM-III-R, GAD in children and adolescents was labeled “overanxious disorder.” This diagnosis was removed from the DSM-IV and GAD is applicable to all age groups.
