Anxiety disorders are marked by excessive fears, nervous affect, and avoidance of a wide range of specific objects and situations. Mechanisms considered critical in the development and maintenance of anxiety disorders are fear arousal that becomes associated with the presence of the particular stimuli, and corresponding relief of anxiety when these situations are avoided (Taylor, Cox, & Asmundson, 2009). Theoretical and empirical evidence supporting the role of fear associations in anxiety disorders has informed the development of exposure therapy, one of the most widely utilized empirically-supported treatments for anxiety disorders (Abramowitz, Deacon, & Whiteside, 2011). Exposure reduces anxiety by creating novel learning experiences with previously feared stimuli in which anticipated negative consequences do not occur. This treatment has been shown to reduce symptoms of anxiety disorders with large effect sizes across numerous diagnoses (Olatunji et al., 2010a and Olatunji et al., 2010b).
While fear is a potent motivator for avoidance in anxiety disorders, it is not the only emotion that prompts this behavioral pattern. Disgust is another prominent emotional state associated with avoidance of distressing stimuli. Disgust is an emotion that evolved to protect humans from ingesting potentially harmful substances (Miller, 1997). In recent years, disgust has been increasingly recognized as a complex emotion that consists of several higher-order components, including reactions specific to violations of the body envelope that remind humans of their mortality or animalistic nature (animal-reminder disgust), moral transgressions (moral disgust), and contamination disgust–the propensity of one disgusting object to transmit disgusting properties to another object (Kelly, 2011 and McKay and Tsao, 2005). Contamination disgust may encompass a range of situations that may or may not involve actual physical contact with a disgusting object, such as: objects that are neutral but come into incidental contact with a disgusting object (“law of contagion”), objects that are neutral but otherwise resemble a disgusting object (“law of similarity”), and objects that are removed from a disgusting object by several points of contact (“sympathetic magic”; Rozin & Fallon, 1987).
Research has shown that disgust plays an important role in the etiology of anxious psychopathology (Olatunji and McKay, 2007 and Olatunji and McKay, 2009). First, at an observational level, the disgust-based concern related to contracting illness and experiencing overt physical harm is reflected in the symptoms of various phobias (Davey, Bickerstaffe, & MacDonald, 2006). The behavioral avoidance characteristic of many anxiety disorders also may be related to disgust, as data shows that many individuals exhibiting anxious avoidance are highly responsive to disgust-based information in the general environment (e.g., Woody & Tolin, 2002). Other evidence has even speculated that the experience of disgust predisposes individuals to negative interpretation bias, therefore contributing to the emergence of anxiety disorders on a general level (Matchett & Davey, 1991).
Data has also implicated disgust in specific anxiety disorders, with the bulk of this work conducted in relation to obsessive-compulsive disorder (OCD; e.g., Olatunji, Tart, Ciesielski, McGrath, & Smiths, 2011). Within the OCD literature, research has suggested that disgust is particularly salient for individuals who experience contamination-related obsessions and compulsions. For example, one study showed that individuals with elevated contamination fears tended to avoid behavioral tasks associated with stimuli that were perceived as disgusting but not actually physically harmful (e.g., drinking from a cup of fresh water with a label affixed reading “saliva sample”), as well as animals that may transmit germs or disease (e.g., holding a live earthworm). Other research has shown that the “sympathetic magic” aspect of contamination disgust is present in individuals with contamination-based OCD symptoms. Compared with non-anxious control subjects, these individuals were more fearful and avoidant of a potentially contaminated object even when it was many steps removed from the contamination source in behavioral avoidance tests using a pencil that touches a contaminant, which in turn touches another pencil, then touches a different pencil, and so on (Tolin, Worhunsky, & Maltby, 2004). Similar evidence was also found in an undergraduate sample, in which students with elevated contamination fears exhibited more avoidance of behavioral tasks involving “sympathetic magic” than individuals with elevated trait anxiety (Tsao & McKay, 2004).
Further tests of the specificity of disgust in contamination-based OCD symptoms have shown this direct link to exist independent from the effects of anxiety (Moretz & McKay, 2008). Other studies have replicated this unique and significant relation between disgust and contamination fear after controlling for negative affect (Olatunji, Moretz et al., 2010). Finally, higher levels of disgust sensitivity have been associated with more stable and persistent contamination fears in growth curve analyses (Olatunji, Moretz et al., 2010).
Although a majority of the literature examining disgust in OCD has focused on the connection between disgust and contamination-based OCD, disgust seems to be involved in other symptom presentations of OCD as well. Elevated disgust sensitivity has been associated with the frequency and severity of general obsessionality (Thorpe, Patel, & Simonds, 2003), findings which have been replicated several times (David et al., 2009 and Olatunji et al., 2009). Other work has also extended the findings of relations between disgust and general obsessionality checking (David et al., 2009) and harm avoidant (Olatunji et al., 2009) OCD symptom presentations more specifically.
In addition to the evidence supporting the importance of disgust in the etiology and maintenance of OCD and other anxious psychopathology in adults, a small, yet, burgeoning body of research has associated disgust specifically with childhood anxiety disorders. It has been suggested that, as has been shown in adults, disgust plays a role in the pathogenesis of childhood anxiety (Muris et al., 2002 and Muris et al., 1999). Experimental data has demonstrated that disgust mediates fear-related beliefs, leading to avoidant behavior (Muris et al., 2009) and anxious interpretation bias towards novel stimuli (Muris, Huijding, Mayer, & de Vries, 2012) in children. Other evidence even suggests that disgust propensity may be transmitted inter-generationally beginning as early as infancy with a mother's verbal and nonverbal displays of disgust in the presence of her child (Muris, Mayer, Borth, & Vos, 2013). However, it is worth noting that in another study, disgust failed to show an independent association to anxiety disorders when evaluated along with trait anxiety (Muris, van der Heiden, & Rassin, 2008), suggesting that disgust mechanisms alone may not be sufficient to explain the emergence of pediatric anxiety disorders.
Research shows that in the treatment of adults with anxiety disorders, disgust reactions are either resistant to treatment or slower to respond to in vivo exposure ( Mason and Richardson, 2012 and McKay, 2006) in comparison to fear responses. Recent quasi-experimental research has corroborated that disgust does indeed respond to exposure at a slower rate than fear, albeit only when study participants endorsed high contamination aversion ( Adams, Willems, & Bridges, 2011), indicating a probable mediation role of contamination aversion in predicting treatment outcome for disgust-related anxiety. Yet despite the evidence that disgust does not respond as well to exposure therapy as does fear, studies have shown that decreases in disgust are key to symptom reduction in individuals with OCD ( Olatunji et al., 2011). Taken together, these findings call for continued research on the treatment of disgust in order to improve anxiety treatment outcomes. Further, while there is much data demonstrating empirical support for childhood anxiety treatments (e.g., exposure therapy), there has been little work exploring whether these interventions are efficacious for childhood anxiety disorders that present with prominent disgust components. Specifically, clinical evaluations of the reduction of disgust in children at treatment completion have yet to be conducted.
This study aims to expand disgust-related research and its associations to anxiety disorders to children samples. The purpose of this study is twofold: (1) to evaluate level of disgust propensity in children with OCD compared to children with other anxiety disorders at baseline, and (2) to compare the role of reductions in disgust propensity following treatment in children with OCD versus other anxiety disorders. We hypothesized that cognitive-behavioral therapy with an emphasis on exposure therapy would reduce disgust propensity across anxiety disorders, but particularly for OCD.
