Revised Reinforcement Sensitivity Theory and Binge Eating: An investigation into the role of the behavioural inhibition system, rash impulsivity, affective states and mindfulness on forms of overconsumption

Abstract

Binge eating has become increasingly common in the general population over the last few decades. The behaviour refers to the consumption of an objectively large amount of food in a short time period whilst experiencing a subjective loss of control over one’s intake, and forms part of the diagnostic criteria for several eating disorders (ED; i.e., binge eating disorder [BED)], bulimia nervosa [BN], anorexia nervosa [AN-Binge-eating/Purge subtype]). Binge eating is associated with a range of adverse physical and psychological complications, and has a significant cost economically. Accordingly, research has increasingly focussed on binge eating to further understand the behaviour and guide interventions. The current thesis aimed to investigate binge eating and overconsumption using revised Reinforcement Sensitivity Theory (RST), a biologically-based theory of personality, which is based on the sensitivity of brain systems that responds to rewarding and punishing stimuli. The broad objective of the thesis was to further understand the individual differences involved in maladaptive eating behaviours and investigate how this information may be useful in guiding intervention strategies. The goal of the thesis was to investigate the mechanisms involved in binge eating and other forms of overconsumption from a RST perspective. The first study investigated similarities and differences in reinforcement sensitivities across ED subtypes and healthy controls, using a measure of revised RST. In the study, 109 adult women with a past or present Anorexia Nervosa-Restrictive subtype (AN-R) diagnosis, 132 with a past or present binge-type ED diagnosis, and 133 non-ED controls, completed a measure of revised RST and measures of disordered eating behaviours and attitudes. Results showed both the AN-R and binge-type group participants scored higher on measures of the Behavioural Inhibition System (BIS) and the Fight/Flight/Freeze System (FFFS) compared to healthy controls. The binge-type group scored higher on measures of rash impulsivity relative to the AN-R and healthy control group, and lower on measures of goal-drive persistence relative to the healthy controls. The AN-R group demonstrated lower reward interest and reward reactivity than the non-ED controls. Being the first study to use a measure in line with the latest developments in RST, these results provided some clarification about the nature of approach behaviour in eating disorders. The key findings implicated high rash impulsivity and low goal drive persistence in binge eating behaviours, whereas no group differences were found for binge-type groups compared to healthy controls or AN-R on measures of reward sensitivity. Another key finding was the transdiagnostic role of BIS and FFFS across ED subtypes. Following these results, the remainder of the thesis aimed to investigate the pathways and conditions under which RST systems influences maladaptive eating behaviours. Thus, the second study investigated the role of negative affect as a mediator between the RST systems and binge eating symptoms. Undergraduate students (n = 229) completed selfreported measures of revised reinforcement sensitivities, negative affect and binge eating symptoms. Indirect pathways from BIS, FFFS and rash impulsivity and binge eating through negative affect were tested. Results showed that negative affect mediated the pathway from BIS to binge eating and rash impulsivity to binge eating, but not from the FFFS to binge eating. The key findings from Study 2 provided further support that BIS and rash impulsivity are particularly relevant to binge eating and made the novel contribution of implicating negative affect as a mechanism of action in this pathway. The first and second studies implicated rash impulsivity and BIS in binge eating and suggested that an interaction between the two systems may be related to binge eating. Study 3 sought to test this interaction and investigate potential protective factors in the pathway to maladaptive eating behaviours. Specifically, Study 3 investigated the moderating effect of rash impulsivity on the pathway from BIS to both binge eating and grazing behaviours. Further, it tested trait mindfulness as a moderating factor in the BIS/Impulsivity pathway to two types of eating behaviour: binge eating; and grazing. Undergraduate students (n = 245) completed self-report measures of BIS, rash impulsivity, trait mindfulness, binge eating and grazing. Results showed a two-way interaction for binge eating, and a three-way interaction for grazing. For binge eating, the relationship between BIS and binge eating grew stronger as rash impulsivity increased, whereas for increasing levels of mindfulness the relationship between BIS and binge eating was reduced. For grazing, results showed that the conditional effect of the BIS x impulsivity interaction on grazing scores varied according to mindfulness. At moderate to high levels of mindfulness, the conditional effect of the BIS x impulsivity interaction on grazing scores was non-significant. At low levels of mindfulness the conditional effect of the BIS x impulsivity interaction on grazing scores was significant, such that the relationship between BIS and grazing grew stronger as did impulsivity. The findings provided further support for the key role of both BIS and rash impulsivity in maladaptive eating behaviours, with the study being the first to apply an RST framework to grazing behaviour. Another key finding was the role of mindfulness as a potential protective mechanism in the pathway between personality risk factors and maladaptive outcomes. The fourth study aimed to extend upon the existing cross-sectional results, by using experimental methodology to investigate the casual effect of the relationship between personality, affective states, mindfulness and eating behaviour. Undergraduate students (n = 245) participated in a laboratory study, where mood was induced (positive, anxiety, neutral), followed by half the participants completing a brief mindfulness exercise (mindfulness, control) before undertaking a bogus taste test to measure food intake. Participants also completed a measure of rash impulsivity to test the interaction between impulsivity, affective state, and mindfulness on food intake. Results showed a three-way interaction, demonstrating that for those participants in the positive mood condition, increased rash impulsivity predicted reduced food intake in the mindfulness condition, whereas rash impulsivity was associated with increased food intake it the control condition. There was no such interaction in the anxiety condition, which was not consistent with the hypothesis for this condition. The key findings from this study supported recent evidence associating positive mood with food intake and added to the literature by highlighting the role of mindfulness and rash impulsivity when interacting with positive mood. The non-significant findings with respect to the anxiety condition, whilst consistent with previous experimental data, are inconsistent with both naturalistic studies and theories of negative affect and eating, raising concerns about the ecological validity of the laboratory food test. The collective key findings from the thesis make several novel contributions to the literature. The use of a recent measure of RST throughout the studies highlights the utility and advantage of using a measure reflective of the revised theory. For the first time binge eating has been evaluated with results that can be interpreted as per the current conceptualisation of RST, and distinction made between the influence of rash impulsivity and reward sensitivity, and BIS and FFFS. The current results highlight the combination of BIS and rash impulsivity are of influence in binge eating, with negative affect a mediator of this pathway. Additionally, the role of mindfulness as a protective factor in buffering against the maladaptive outputs of RST systems was demonstrated, with differing effects dependent on the specific eating behaviour (e.g., binge eating, grazing, food taste test). Collectively, these results progress the field through a series of novel findings that allow for a deeper understanding of RST and eating behaviour. The findings from this thesis highlight areas in which future research is warranted, and the clinical implications may inform the development and extension of both treatment and prevention approaches.