Generalized anxiety disorder (GAD) and substance use disorders (SUDs) are highly comorbid, and GAD–SUD comorbidity is associated with a host of poor psychosocial outcomes, including higher rates of hospitalization, disability, functional impairment, and inferior GAD and SUD treatment outcomes. Despite the noted severity of this group and clinical implications, current research is limited in a few distinct ways; studies have rarely utilized a longitudinal design and non-treatment seeking individuals to examine how GAD comorbidity impacts SUD outcomes over time. The current study utilized a nationally representative sample of individuals in the U.S. assessed in the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) at Wave 1 (2001–2002) and Wave 2 (2004–2005), comparing individuals who met criteria for both DSM-IV past year GAD and SUD (n = 286) and those who met criteria for past year SUD only without GAD (n = 5730) at Wave 1. Results indicated that GAD–SUD individuals were significantly more severe than the SUD only group across almost all outcomes assessed (with the exception of alcohol frequency); individuals with GAD–SUD had a more severe psychiatric history, worse health-related quality of life at both waves, greater incidence of new Axis I disorders, higher rates of treatment seeking, and greater self-reported drug use at the follow up. The current study is the first to compare individuals with SUD with and without comorbid GAD over time using a nationally representative sample. Findings further support the clinical severity of this group and suggest the need for GAD–SUD treatment options.
Generalized anxiety disorder (GAD) and substance use disorders (SUDs) are highly comorbid (Conway et al., 2006; Grant et al., 2004 and Grant et al., 2005; Kessler et al., 2005), and individuals with GAD–SUD comorbidity have significantly worse outcomes than single-diagnosis counterparts (Smith and Book, 2010). The presence of co-occurring GAD is associated with heavy drinking, poor social adjustment and functioning, greater disability, and frequent hospitalizations (Burns et al., 2005; Grant et al., 2005). Comorbid GAD, particularly excessive worry, also significantly interferes with substance abuse treatment (Smith and Book, 2010). Compared to other anxiety disorders, GAD seems to be more strongly related to current substance use and associated with greater levels of impairment. In an examination of the relationship between 12-month drug dependence and commonly co-occurring anxiety disorders (i.e., GAD, panic disorder with and without agoraphobia, social phobia, specific phobia), only GAD was significantly related to 12-month drug dependence (as opposed to the other anxiety disorders), even after controlling for other comorbid psychiatric disorders (Compton et al., 2007). Further, even in its pure form, GAD is associated with significantly higher rates of disability and impairment compared to other anxiety disorders (Grant et al., 2005). GAD–SUD comorbidity clearly represents a significant clinical challenge due to the severity of symptoms and poor treatment response.
Despite the clinical implications of GAD–SUD comorbidity, a few limitations have hindered research in this area including: (1) studies have largely focused on anxiety disorders more generally and their co-occurrence with SUDs, rather than focusing more exclusively on GAD to enable specificity of understanding (cf., Alegria et al., 2010; Grant et al., 2005); and (2) research has been somewhat narrowly focused on clinical samples (Bruce et al., 2005; Smith and Book, 2010). As one step to address these limitations, Alegria et al. (2010) examined psychiatric comorbidity and other clinical correlates in a sample of individuals with GAD, comparing those with and without SUD. The study found that individuals with GAD–SUD demonstrated higher levels of comorbidity, substance use, and disability. This cross-sectional study highlighted the severity of the GAD–SUD group and suggested the need for longitudinal studies to examine outcomes over time. A second important future direction included testing how comorbid GAD affects substance use outcomes, as studies have largely focused on how SUD comorbidity affects GAD outcomes (Alegria et al., 2010; Bruce et al., 2005).
