April 20, 2015 /
Background: Generalized anxiety disorder (GAD) is common in multiple sclerosis (MS) but understudied. Reliable and valid measures are needed to advance clinical care and expand research in this area. The objectives of this study were to examine the psychometric properties of the 7-item Generalized Anxiety Disorder Scale (GAD-7) in individuals with MS and to analyze correlates of GAD.
Methods: Participants (N = 513) completed the anxiety module of the Patient Health Questionnaire (GAD-7). To evaluate psychometric properties of the GAD-7, the sample was randomly split to conduct exploratory and confirmatory factor analyses.
Results: Based on the exploratory factor analysis, a one-factor structure was specified for the confirmatory factor analysis, which showed excellent global fit to the data (χ212 = 15.17, P = .23, comparative fit index = 0.99, root mean square error of approximation = 0.03, standardized root mean square residual = 0.03). The Cronbach alpha (0.75) indicated acceptable internal consistency for the scale. Furthermore, the GAD-7 was highly correlated with the Hospital Anxiety and Depression Scale–Anxiety (r = 0.70). Age and duration of MS were both negatively associated with GAD. Higher GAD-7 scores were observed in women and individuals with secondary progressive MS. Individuals with higher GAD-7 scores also endorsed more depressive symptoms.
Conclusions: These findings support the reliability and internal validity of the GAD-7 for use in MS. Correlational analyses revealed important relationships with demographics, disease course, and depressive symptoms, which suggest the need for further anxiety research.
From the Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, WA, USA (ALT, NH, MB, RS, KA); and Veterans Affairs Puget Sound Health Care System, Multiple Sclerosis Center of Excellence West, Seattle, WA, USA (NH).
Correspondence: Alexandra L. Terrill, PhD, 1959 NE Pacific St., Box 356490, Seattle, WA 98195; e-mail: aterrill@u.
Multiple sclerosis (MS) is a chronic neurologic disorder that affects the central nervous system and produces physical, cognitive, and psychological symptoms. Most psychological research in MS focuses on the high prevalence of depression1; however, a small body of research suggests that anxiety disorders might be more common.1–3Unfortunately, anxiety is infrequently studied in MS, and the existing literature is challenging to synthesize owing to a variety of definitional, methodological, and assessment variations.
Anxiety disorders are the predominant mental health condition in the general population and in individuals visiting a medical provider.4,5 Generalized anxiety disorder (GAD) is the most common diagnosis and is characterized by excessive and persistent anxiety and worry.6 The point prevalence is approximately 6.2% in the general population7 and 8% in primary care.8 Among individuals with MS, the point prevalence is as high as 19%.9
In MS, GAD is associated with confirmed exacerbations, pseudo-exacerbations,10 poor medication adherence,11 overuse of health-care services, and lower quality of life.12Suicide, suicidal ideation, and self-harm are also associated with GAD in MS.13Although there are no treatment studies specifically for GAD in MS,14 successful remission of symptoms was demonstrated in primary-care patients.15 Therefore, early detection through screening for GAD symptoms may lead to improved treatment and long-term outcomes via earlier initiation of pharmacologic or behavioral interventions.
Until relatively recently, there was an absence of validated, brief screening instruments for GAD in the general population and primary care. The 7-item Generalized Anxiety Disorder Scale (GAD-7) was developed to fill this gap, serving as a brief questionnaire based on the GAD criteria found in the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision) (DSM-IV-TR).6 This measure was validated in primary-care patients and further in international populations,16 the general population,17 psychiatric populations,18 and geriatric populations.19 Although the GAD-7 is used in MS,20 the psychometrics of the measure have not been evaluated.
Given the high occurrence and impact of GAD on individuals with MS, it would be useful to examine the utility of GAD screening instruments for clinical and research purposes in this population. To our knowledge, there is no validated screening measure for GAD in this population. The closest validated screen is the Hospital Anxiety and Depression Scale (HADS).21 Although the HADS effectively screens for generalized anxiety in patients with MS,21 the original intent of this screen was not focused on GAD.22 It is also copyright protected and must be purchased. Conversely, the GAD-7 is free, is readily accessible,23 and aligns with the diagnostic criteria for GAD. However, because the GAD-7 includes somatic symptoms, which may overlap with symptoms of MS, it is unclear whether this screen is an effective measure of GAD symptoms in MS populations.
The present study was conducted to 1) examine the psychometric properties of the GAD-7 to determine its appropriateness for use in individuals with MS and 2) analyze correlates of GAD symptoms in individuals with MS. The identification of a scientifically viable measure of GAD for people with MS can potentially serve as the foundation for improved clinical assessment and future research on GAD in this population.
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