Paper that makes the case for a psychological explanation for CFS (and its flaws) Psychological symptoms, somatic symptoms, and psychiatric disorder in chronic fatigue and chronic fatigue syndrome: a prospective study in the primary care setting, 1996 (pdf). The study may be 15 years old but Simon Wessely and Peter White still like to quote its findings to support a psychological explanation for CFS. This paper strongy links CFS with psychiatric disorders, implies that both fatigue and symptoms of the illness are primarily due to psychiatric disorder, and suggests that CFS is not a specific illness, just one end of a spectrum of chronic fatigue. Essentially, it says that both fatigue and psychosomatic symptoms accumulate with psychogical morbidity until 'hey presto', some people cross an arbitrary threshold and are defined as having CFS. Method is as described in post #7 and note that 'somatic symptoms', including CDC-94 symptoms, are assessed too. The fundamental flaw in this study is that while CFS is defined by unexplained fatigue, the paper fails to distinguish betweeen fatigue that is unexplained and fatigue that is explained. In fact: Since fatigue is common to many illnesses, both physical and psychological, it seems likely that in many cases the principal complaint would explain the chronic fatigue. For example, depression is common in primary care setting and one of the main symptoms of depression is fatigue. In contrast to other studies, only 1.5% of chronic fatigue patients were excluded for explained fatigue, which might be because they weren't given a proper clinical evaluation and because the authors don't seem to consider any psychological disorder an explanation for fatigue. The authors say: And that's the problem. This study tells us little about CFS where the fatigue has to be unexplained. The strong correlation between fatigue and psychological morbidity does not explain CFS. I will post later in more detail on the correlation between symptoms and 'psychological morbidity'. However, the main point is that the correlation might be interesting if it was for those with unexplained fatigue, but without that qualificiation it tells us little. CFS cases The study also finds a strong link between psychological morbidity and full-blown CFS. To show a causal link they point out that 5 out of the 6 NEW cases of CFS (ie patients who were not fatigued at the start of the study) had previously had a psychiatric diagnosis. Similarly, 5 out of 6 new CFS cases had previously been prescribed psychoactive medication. This can be seen as further evidence of a strong link between pyschological morbidity and CFS. Alternatively, it can be seen as further evidence of poor diagnosis leading to inclusion of too many patients with psychologically caused fatigue and a false prevalence rate of 2.5%. Conclusion Failure to properly define the patients by excluding cases of explained chronic fatigue makes the findings of this study unreliable. The paper merely confirms the known link between chronic fatigue and psychological morbidity, while throwing little light on the nature of CFS.