An examination of the bidirectional relationship between functioning and symptom levels in patients with anxiety disorders in the CALM study

Anxiety disorders are associated with pervasive functional impairment. The cost to society in income or productivity loss for patients who meet criteria for one of these disorders was $46.6 billion in 1990 (DuPont et al. 1996). In addition to the financial burden, patients with anxiety disorders experience interpersonal problems such as marital discord and other family and social problems (Markowitz et al. 1989; Lochner et al. 2003), education problems (Stein et al. 1997; Wittchen et al. 2000), and increased use of non-prescription drugs (Lochner et al. 2003). Thus, the functional impairment associated with anxiety disorders is as important to understand and address as the symptoms of anxiety. Throughout this paper, for the sake of clarity, symptoms will be referred to throughout as anxiety and depression characteristics that are operationalized in the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 2013), including physical, behavioral, and cognitive disturbances. Functioning will refer to activities of daily living such as the ability to work or attend school, or fulfill social or familial obligations. The relationship between symptom severity and functional impairment in patients with anxiety disorders is not as straightforward as might be expected. For instance, while the majority of studies demonstrate that the frequency of panic attacks or number of depression symptoms is predictive of disability (Katerndahl & Realini, 1997; Rubin et al. 2000; Chan et al. 2009), others have found that the frequency of panic attacks is not correlated with functioning (Michelson et al. 1998). In addition, the number of anxiety symptoms endorsed accounts for only a small percentage of variance in quality of life or functioning (Leon et al. 1992; Michelson et al. 1998; Rapaport et al. 2005). These data suggest that improvements in functioning are unlikely to occur merely through symptom reduction. Improvement in functioning is often measured as a sign of treatment effectiveness. A number of studies of pharmacological treatment report significant improvements on measures of functioning alongside improvements on symptom measures for anxiety disorders (Jacobs et al. 1997; Lecrubier & Judge, 1997; Mavissakalian et al. 1998; Michelson et al. 1998; Malik et al. 1999; Stein et al. 1999). However, the situation is complicated by other studies that fail to find differences in functioning between patients receiving medication versus placebo (Hoehn-Saric et al. 1993) or find differences on self-report measures of functioning but fail to find differences on clinician-rated measures of functioning (Michelson et al. 1998). Evidence for changes in functioning from pre- to post- cognitive behavior therapy (CBT) is more limited, particularly compared to other active treatments, but several studies indicate improved quality of life for patients with anxiety disorders following CBT (Safren et al. 1996; Moritz et al. 2005; Arch et al. 2012). Some studies indicate equivalent improvements in functioning following CBT compared to pharmacotherapy (Kilic, Noshirvani, Basoglu, & Marks, 1997). Few studies have attempted to parse the complicated relationship between symptom levels and functional impairment. Those that have only examine unidirectional relationships, typically by examining whether improvements in symptom levels predict improvements in functioning. The results from such studies have been contradictory. On the one hand, several studies show that symptom improvements are associated with, or predict, functional improvement, following pharmacotherapy (Jacobs et al. 1997) and CBT (Telch et al. 1995; Moritz et al. 2005). On the other hand, other studies fail to substantiate the link between symptom and functional impairment outcomes (Tenney et al. 2003; Monson et al. 2006). No study to our knowledge has simultaneously analyzed the predictive role of symptom improvement on functioning while examining the role of functional improvement on symptom alleviation. This is an essential question that has clear implications for treatment development. If functional improvement is a stronger predictor of symptom reduction than the converse, then clinicians would be encouraged to target ways of improving functioning in patients’ daily lives early in the treatment process. Alternatively, if symptom alleviation more strongly predicts functional improvement, clinicians would be justified in dedicating more time to targeting symptom alleviation from the onset of treatment. The current study aimed to evaluate the bidirectional nature of the relationship between symptoms and functioning. We used data from a sample of patients with principal anxiety disorders presenting to their primary care physicians as part of the Coordinated Anxiety Learning and Management (CALM; Roy-Byrne et al. 2010; Craske et al. 2011) study. Analyses were conducted on data covering an 18-month period, providing an extended time period to capture changes in both functioning and symptoms. The primary hypothesis was that symptom levels at a given time point would predict functioning at the subsequent time point, and simultaneously that functioning at a given time point would predict symptom levels at a subsequent time point.