Effective Behavioural Strategies for Reducing Disgust in Contamination Fears

Abstract

Disgust has been implicated in the aetiology and maintenance of various forms of psychopathology, including contamination related obsessive-compulsive disorder (C-OCD). Disgust is difficult to diminish using standard exposure-based interventions. It can be acquired through evaluative conditioning (EC) where a disgust valence towards a neutral stimulus (CS) can be learnt through its contingent presentation with a disgusting stimulus (US). Drawing on the expectancy learning model, exposure-based interventions successfully reduce fear towards the CS by violating danger expectancy, but the affective valence of the CS is less impacted by similar methods. Strategies utilising evaluative conditioning directly target valence of the CS-US relation by repeated presentations of the stimulus of positive valence along with CS (i.e., in counterconditioning) or with US (i.e., in US revaluation). This thesis compared the effects of exposure-based and EC-based strategies in reducing disgust across healthy adults and C-OCD analogue samples. Study 1 compared the effects of exposure in reducing disgust and danger expectancy with EC-based interventions in a sample of students using a picture pairing paradigm. It was found that disgust was acquired through EC, as indicated by both self-report and EMG data. It was further found that at the subjective level, disgust was effectively diminished by all interventions with an exception of a control group. EC-strategies showed larger effect sizes in reducing disgust, while exposure-based interventions showed greater effect sizes in reducing US expectancy. Only counterconditioning reduced EMG levator activity associated with disgust at extinction phase. However, participants in this group showed increased scores on contamination and checking OCD subscales. After controlling for these variables, EMG levator activity remained increased at extinction but unaffected by the intervention. The findings suggested possible differential disgust conditioning effects between individuals scoring high and low on the contamination- and checking- related OCD measures. Study 2 investigated the effects of counterconditioning in a sample of healthy university students in comparison to those scoring in the clinical range for C-OCD symptomatology. Using the same picture pairing paradigm, Study 2 replicated the findings that repeated presentation of neutral stimulus (CS) with the disgusting one (US) leads to the transfer of affective disgust valence onto the CS, which supported an EC effect across both groups. However, students with C-OCD symptomatology self-reported greater danger expectancy after acquisition. The experimentally induced CS disgust was effectively reduced across both groups when subjective ratings were compared. The disgust specific EMG ratings were reduced by counterconditioning only, although this may have been partially affected by a lack of power in the EMG analysis. Nevertheless, the study indicated potential differential conditioning effects between healthy and C-OCD analogue samples. Finally, a series of case studies was utilised in Study 3 and compared the effects of counterconditioning with exposure with response prevention (ERP) across 6 participants with C-OCD symptomatology. The aim was to understand how optimized ERP and counterconditioning changes disgust, fear and avoidance to intrinsically selected CSs in a cross-over design. Robust improvement rate difference analysis revealed immediate reductions in self-reported disgust following counterconditioning as opposed to ERP. Danger expectancy ratings and avoidance towards the CS reduced significantly regardless of the interventions for most participants. Despite several limitations described in this document, the present research program shows important preliminary findings regarding the effects of disgust conditioning and the effectiveness of different behavioural interventions across healthy and C-OCD analogue student samples. Overall, counterconditioning seems to be a promising strategy in reducing disgust-based responses in participants scoring in the clinical range on C-OCD symptomatology. Implicating counterconditioning in the current C-OCD treatment could improve treatment effects and reduce relapse rates. Future research, however, should replicate these findings in larger samples of clinically diagnosed C-OCD patients.