Aetiopathogenesis and Phenomenology of Medically Unexplained Conditions
Functional somatic syndromes (FSS) are characterised by the presence of somatic symptoms and the absence of any demonstrable abnormalities of organ structure or function that would allow an attribution to a conventionally defined medical disease. There are numerous case definitions for different FSS...
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|Summary:||Functional somatic syndromes (FSS) are characterised by the presence of somatic symptoms and the absence of any demonstrable abnormalities of organ structure or function that would allow an attribution to a conventionally defined medical disease. There are numerous case definitions for different FSS, including chronic fatigue syndrome, fibromyalgia syndrome, or irritable bowel syndrome; however, to date, these do not have the status of nosological entities. The reason for this is that there is no universal consensus on how FSS should best be understood. The most extreme positions are those held by “lumpers”, who advocate the concept of one general FSS, and “splitters”, who are in favour of a concept that distinguishes between specific FSS (so-called “one versus many debate”). The overall aim of this thesis was to identify similarities and differences of FSS by studying aetiopathogenetic and phenomenological characteristics across a variety of syndromes. Concerning aetiopathogenesis, the role of stress was of particular interest. Based on the literature, a framework was postulated that illustrated the role of psychobiological stress in the development and maintenance of FSS. Specific parts of this framework were empirically tested and integrated. Concerning phenomenology, a number of syndromes was measured concomitantly to evaluate their overlaps, the role of depression and anxiety, and the latent structure of somatic symptoms. Different patient samples were recruited and a multi-methodological approach was adopted, including experimental, ambulatory assessment, and survey research designs. In sum, stress was confirmed as a factor that is involved in the predisposition, precipitation, and perpetuation of FSS in different patient samples; important mechanisms underlying this relationship were identified (studies I to III). Despite this commonality, syndrome overlap was rather low when the approach to case identification excluded clear-cut medical explanations for somatic symptoms (studies IV and V). This apparent discrepancy was reflected by the fact that symptoms pertaining to FSS could best be explained by a general and four symptom-specific factors (studies VI). Based on the findings of this thesis, the greatest confidence may be placed in stating that FSS are "one and many". It is conceivable that a high amount of stress during childhood or adulthood and subsequent alterations in stress-responsive systems as well as the cognitive style of somatoensory amplification represent endophentotypes that are common to medically unexplained conditions in general. The identified symptom-specific factors would then need to be understood as phenomenological variants of this process. Future attempts at classifying medically unexplained conditions should acknowledge both common and symptom-specific factors in order to foster prolific research.|