Psychological characteristics associated with food avoidance behaviour and perceived (non-­‐medically diagnosed) food intolerance in Australia

Abstract

Background: The aim of this thesis was to increase understanding of the discrepancy reported in the literature between perceived and medically diagnosed food intolerance. It also addressed the emerging trend in modern health decision making towards self-diagnosis and self-management of symptoms through the use of non‐medically supervised exclusion diets. The hypothesis was investigated that specific individual‐level psychological characteristics may underpin this phenomenon. Of particular interest was to explore factors, which are associated with the belief that reported symptoms are due to an intolerance or sensitivity to certain foods, in the absence of formal medical diagnosis. Underlying this was the question whether the psychogenic characteristics previously associated with perceived food intolerance in mostly clinical studies, which are thought to result in the misperception and misattribution of symptoms, could be generalised to people with perceived food intolerance in the general population. Aims of the thesis: • To extend understanding of predictors of food avoidance in the Australian adult population beyond wheat avoidance to dairy avoidance. As part of that to investigate the symptoms, diagnoses and the potential for misattributions leading to self-prescribed food avoidance (Study 1). • To explore the associated symptoms, the sources of diagnosis, and the psychological predictors of reporting of non‐medically diagnosed (NMD) and medically diagnosed (MD) food intolerances in the Australian population (Study 2). • To explore whether somatosensory amplification, described in previous research as a predisposing condition that leads to perceived food intolerance through the process of somatisation, is potentially a response to the experiencing of very severe symptoms, rather than a cause of the condition and its symptoms (Study 3). Results: Study 1 The avoidance of dairy appeared to rely substantially on a NMD connection between ingestion and symptoms, and was associated with increased reporting of past food intolerance. It was also predicted by worry about illness. These findings raised questions regarding the individual-level characteristics that may predispose individuals to attribute symptoms to the consumption of certain foods and, without a medical diagnosis, to subsequently label themselves as food intolerant. They also directed attention to the possible contribution of illness worry to the amplification and misattribution of these symptoms. Study 2 found that many adult Australians classify themselves as food intolerant without a supporting medical diagnosis. Having a NMD intolerance was associated with increased receptiveness to complementary and alternative medicine. Null effects for neuroticism cast doubt on the role of anxiety and negative affect suggested by clinical research. The found association of somatosensory amplification with both MD and NMD intolerances indicates that extra‐vigilance in respect of symptoms is not peculiar to the latter. Study 3 revealed that the tendency to amplify symptoms and attribute them to a threatening disease was weaker in patients reporting food intolerance than those reporting IBS, with or without food intolerance. The findings support the view that severity and amplification of symptoms are markers of IBS‐like symptoms and are not peculiar to the perception that one has a food intolerance. Conclusions: The findings in this thesis supports the view that perceived food intolerance is unlikely to be a phenomenon, the result of psychiatric disturbance. Attributing adverse symptoms to specific foods is also unlikely to be due to psychosomatic reactions, of the kind observed in functional somatic syndromes. The origins of this behaviour appear to fall outside the mainstream medicinal practice, with significant adherence to complementary and alternative medicine, and notable rejection of doctor’s advice. This may reflect a tendency of people to exercise control over their health and to feel responsible for managing the risks of presumed food intolerance, without the need for medical evidence or oversight.