Elsevier

Journal of Affective Disorders

Volume 190, 15 January 2016, Pages 310-315
Journal of Affective Disorders

Research report
Low stability of diagnostic classifications of anxiety disorders over time: A six-year follow-up of the NESDA study

https://doi.org/10.1016/j.jad.2015.10.035Get rights and content

Highlights

  • Anxiety disorder diagnoses have low longitudinal stability.

  • Diagnostic stability at a chronic course was lower than at a non-chronic course.

  • The validity of the different anxiety disorder categories is not supported.

  • A more dimensional approach to the classification of anxiety disorders is proposed.

Abstract

Background

Stability of diagnosis was listed as an important predictive validator for maintaining separate diagnostic classifications in DSM-5. The aim of this study is to examine the longitudinal stability of anxiety disorder diagnoses, and the difference in stability between subjects with a chronic versus a non-chronic course.

Methods

Longitudinal data of 447 subjects with a current pure anxiety disorder diagnosis at baseline from the Netherlands Study of Depression and Anxiety were used. At baseline, 2-, 4-, and 6-year follow-up mental disorders were assessed and numbers (and percentages) of transitions from one anxiety disorder diagnosis to another were determined for each anxiety disorder diagnosis separately and for subjects with a chronic (i.e. one or more anxiety disorder at every follow-up assessment) and a non-chronic course.

Results

Transition percentages were high in all anxiety disorder diagnoses, ranging from 21.1% for social anxiety disorder to 46.3% for panic disorder with agoraphobia at six years of follow-up. Transition numbers were higher in the chronic than in the non-chronic course group (p=0.01).

Limitations

Due to the 2 year sample frequency, the number of subjects with a chronic course may have been overestimated as intermittent recovery periods may have been missed.

Conclusions

These data indicate that anxiety disorder diagnoses are not stable over time. The validity of the different anxiety disorder categories is not supported by these longitudinal patterns, which may be interpreted as support for a more pronounced dimensional approach to the classification of anxiety disorders.

Introduction

Anxiety disorders are common and impose a considerable burden on those affected as well as on their relatives and society (Berger et al., 2012, De Graaf et al., 2012, Plaisier et al., 2010, Senaratne et al., 2010, Wittchen, 2002). A range of anxiety disorders that differ in their specific symptom patterns is distinguished in the subsequent versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM), including the latest version, the DSM-5 (American Psychiatric Association, 2013). The DSM-classification system contains ‘simple reliable rules for categorical assignments required for clinical and research purposes' (Shear et al., 2007). Still, symptoms such as panic attacks and avoidance behavior as well as impairment are shared between diagnoses and across diagnostic boundaries, leading to high comorbidity between different anxiety disorders (Batelaan et al., 2012, Knappe et al., 2013, Kroenke et al., 2007, Shear et al., 2007). For this reason, a dimensional approach of describing mental disorders is receiving increasing attention (Andrews et al., 2008). As a possible approach, Shear et al. (2007) suggested a ‘hybrid categorical-dimensional model’, which would both be clinically useful and provide a better understanding of symptoms that are found across diagnoses. One of the proposals for maintaining separate diagnoses of social anxiety disorder, panic disorder with and without agoraphobia, agoraphobia, generalized anxiety disorder and other anxiety disorders is their presumed stability, which was listed as an important predictive validator in the ‘Guidelines for Making Changes to DSM-5’ (Kendler et al., 2009).

If the different anxiety disorder classifications are not diagnostically stable across time, and would show many transitions from one anxiety disorder to another, this could indicate that they are not really distinct disorders, but should rather be regarded as one entity with different phenotypes or varying presentations over time. This issue of longitudinal stability of diagnosis has been studied a number of times before, but many questions currently remain unresolved. A five-year follow-up population study of 3021 Germany subjects aged 14–24 years at baseline found a considerable degree of transitions between anxiety and other affective disorders as well as with somatoform and substance use disorders (Wittchen et al., 2000). Remitted cases of baseline social anxiety disorder had an increased risk of developing other anxiety (especially generalized anxiety disorder and panic disorder) and depressive disorders in follow-up. Nay et al. (2013) found in a population study of 43,093 subjects aged 18 years and older that social anxiety disorder at baseline predicted the onset of panic disorder with agoraphobia after three-year follow-up, but not the development of panic disorder without agoraphobia. They also reported that a history of panic attacks, generalized anxiety disorder and/or major depression is a predictor of incidence and relapse of panic disorder with or without agoraphobia. To the best of our knowledge no longitudinal studies examining stability of diagnosis of other anxiety disorders have been published to date. Further, it is not known whether diagnostic transitions would occur more often in subjects with remissions and relapses versus subjects in whom the disorder has a chronic course. Transitions from anxiety to depressive disorder diagnoses and the impact of a comorbid depressive disorder at baseline were not examined. The focus of the current study was to investigate whether transitions from one anxiety disorder diagnosis to another occurred and vice versa, i.e. how do anxiety disorders relate to each other.

The Netherlands Study of Depression and Anxiety (NESDA) has followed up 1101 patients with different anxiety disorders for six years, including diagnostic assessments every two years. Earlier work in NESDA has shown that courses varied for different anxiety disorders (Hendriks et al., 2013), while Scholten et al. (2013) reported that, in case of recurrence, a new anxiety disorder (i.e., a transition from the baseline disorder to the anxiety disorder at follow-up) occurred in 32.7% of the cases. The earlier NESDA publications were based on two year follow-up data. Moreover, stability of diagnosis has not been systematically assessed in pure anxiety disorder categories, distinguishing between either a persistent course (chronic course) or a course with remissions and relapses (non-chronic course). Now, data from four waves, spanning 6 years, are available and will be used to address this issue. The aim of the current study is to determine the longitudinal stability of diagnosis of pure social anxiety disorder, panic disorder with and without agoraphobia, agoraphobia and generalized anxiety disorder. Subjects with a course marked by remissions and relapses are more likely to have a change of diagnosis than subjects with a chronic course. Therefore, the second aim of this study is to look at differences in diagnostic stability between subjects with a chronic versus non-chronic course.

Section snippets

Study sample

The Netherlands Study of Depression and Anxiety (NESDA) is a national study designed to investigate the course and consequences of depressive and anxiety disorders. Briefly, four assessment waves have been completed to date, and the fifth wave is currently ongoing. The study started with 2981 subjects with a mean age of 41.9 years (SD=13.0, range 18–65 years; 66.4% women), including healthy controls (n=652; 22%) and subjects with a past or current depressive and/or anxiety disorder (n=2329;

Descriptives

Sociodemographic characteristics of the 447 subjects in the study sample indicated that the sample consisted of more women than men (70.0% women), in their middle ages (mean age=41.65 years, SD=12.7, range=18–65) with a mean number of years of education of 12.3 (SD=3.17, range=5–18). Compared with subjects with a pure anxiety disorder diagnosis, subjects with non-pure, multiple anxiety disorder diagnoses were characterized by higher Beck Anxiety Inventory and Fear Questionnaire scores, more

Discussion

The aim of the current study was to determine the longitudinal stability of the diagnoses of social anxiety disorder, panic disorder with and without agoraphobia, agoraphobia and generalized anxiety disorder. In case anxiety disorder diagnoses are stable, we expected high stability percentages. In this study we found percentages clearly below 70% or just at the level of 70%. Our findings indicate that pure anxiety disorder diagnoses are not stable over time. Transitions of diagnosis are common

Role of the funding source

The funding sources had no involvement in the study design; in the collection, the analysis and the interpretation of data; in the writing of the report; and in the decision to submit the article for publication.

Acknowledgments

The infrastructure for the NESDA study (www.nesda.nl) is funded through the Geestkracht Program of The Netherlands Organization for Health Research and Development (Zon-Mw, Grant no. 10-000-1002) and is supported by participating universities and mental health care organizations (VU University Medical Center, GGZ inGeest, Arkin, Leiden University Medical Center, GGZ Rivierduinen, University Medical Center Groningen, Lentis, GGZ Friesland, GGZ Drenthe, Scientific Institute for Quality of Health

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