Explaining medically unexplained symptoms-models and mechanisms
Introduction
Medically unexplained symptoms play a major role in most health care systems, and it is dissatisfying that such highly prevalent complaints are considered “unexplained”. This paper aims to summarize the current concepts and mechanisms that underlie physical complaints, to help understand the development and maintenance of symptoms not part of diagnosed medical conditions. We will also discuss the empirical background of these mechanisms. As authors use many different terms for these complaints, we will occasionally provide data from studies using associated diagnoses and concepts, such as somatoform complaints, chronic fatigue syndrome, fibromyalgia, and chronic pain. We will use the terms “somatoform disorders”, “somatization”, and medically unexplained symptoms interchangeably, while focussing on patients with multiple somatic complaints. Conversion and dissociation are not addressed in this review. The major question of the article is, “how can we explain symptoms that are not due to medically recognised diseases?”.
In some cases, studies on hypochondriasis might help to understand processes of symptom development and persistence, and are therefore partially included in this overview. However, it should be kept in mind that only a small portion of patients with somatization syndrome report comorbid hypochondriasis (Rief, Heuser, Mayrhuber et al., 1996). Athough health anxiety scores are increased in this group, it is still possible that the mechanisms involved in hypochondriasis are typical anxiety processes, and not valid for somatization syndrome. Therefore the results from hypochondriasis studies should be generalized to medically unexplained symptoms with caution.
The list of possible mechanisms that may be involved in the development and maintenance of medically unexplained symptoms (MUS) is overwhelming, and a comprehensive overview would go beyond the space limitations of this journal. Therefore this paper focuses on several specific aspects, without attempting to present an all-embracing overview. First, current models that offer a framework for the discussion of single mechanisms are presented. Then, psychological mechanisms and empirical evidence for the development and maintenance of physical complaints are reported. In this section, we provide data on the relevance of symptom attributions, illness beliefs, attention and perception, expectation and memory, and the role of health anxiety and health worries. Then behavioural aspects, such as health care utilization and illness behaviour, avoidance behaviour and physical deconditioning, reassurance-seeking and the role of doctor-patient interaction are highlighted. Following this, the role of emotion regulation, attachment styles and personality is considered; the role of traumatic experience is addressed in another paper in this issue.
Section snippets
Models of medically unexplained symptoms (MUS)
One of the most influential models on multiple unexplained symptoms was first described for hypochondriasis by Barsky & Wyshak (1990). This model focuses on perception and cognition. The authors suggest that hypochondriacs amplify benign somatic sensations and misattribute them to serious diseases. As a consequence, patients focus their attention on bodily processes and experience a broad range of somatic sensations as more intense, more noxious, and more disturbing. This attention-focussing
Cognitive aspects
Most of the models described above focus on the interaction of perceptual and cognitive aspects in the development and maintenance of medically unexplained symptoms (MUS). We will now summarize the empirical evidence for the relevance of cognitive aspects, such as symptom attribution, illness beliefs, attention and perception, expectation and memory bias, as well as health worries, to MUS.
Integration of evidence-based mechanisms
Most models of medically unexplained symptoms emphasize the role of cognitive factors. There is some evidence that patients with MUS over-interpret physical sensations as possible signs of illnesses. Patients with hypochondriasis have demonstrated an over-exclusive concept of health, although this has not been clearly shown in patients with MUS in general. One aspect of cognitive models for patients with MUS definitely needs to be modified: patients with MUS do not have simplistic, monocausal
Conclusion: strengths and empirical validation of the models
In the light of this overview on empirical data, the different models presented in part two of this article show specific strengths and weaknesses. The strength of Barsky's model is its simple formulation, and it can even be used to explain the disorder to patients. The basic mechanisms used in this model, such as attention, perception, and attribution processes have some empirical validation, although the model neglects many other well-validated factors, or offers only indirect explanations
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