Prins et al (Reference Prins, Bleijenberg and Klein Rouweler2005) assessed psychiatric comorbidity in chronic fatigue syndrome (CFS) using the Structured Clinical Interview for DSM–III–R. Comorbidity was remarkably low compared with similar investigations, and in particular the apparent absence of current post-traumatic stress disorder (PTSD) was striking. The authors speculated that the low comorbidity rates might result mainly from a lack of ‘psychiatric bias’ of the examiners. They also found that psychiatric comorbidity did not predict the outcome of cognitive–behavioural therapy.

Without doubt, diagnosing comorbid depression and anxiety disorders in CFS is useful because both are highly treatable emotional reactions to the illness. The relevance of somatoform disorders (such as somatisation disorder) for CFS is more doubtful, given their inherently dualistic character (Reference Mayou, Kirmayer and SimonMayou et al, 2005). Most importantly, the very low lifetime incidence of PTSD reported by Prins et al (Reference Prins, Bleijenberg and Klein Rouweler2005) emphasises the value of descriptive psychiatric diagnoses in CFS. In my experience many patients with CFS report victimisation during childhood and/or adult life, and this has been confirmed by a controlled questionnaire-based study (Reference Van Houdenhove, Neerinckx and OnghenaVan Houdenhove et al, 2001). However, most victimised patients have ‘sub-threshold’ symptoms that do not meet diagnostic criteria of clinical PTSD. It is important to listen carefully to the patient's life history (Reference Van HoudenhoveVan Houdenhove, 2002) in order to shed light on any aetiological role of traumatic experiences in CFS and the resulting personality disturbances that may negatively influence treatment.

In summary, psychiatric evaluation of patients with CFS should not be limited to establishing a diagnosis of psychiatric comorbidity but should first involve narrative strategies (Reference Greenhalgh and HurwitzGreenhalgh & Hurwitz, 1998).