Different definitions of chronic fatigue syndrome (CFS) have different psychiatric exclusion criteria and this affects the type and frequency of associated psychiatric morbidity found. The operational criteria for neuraesthenia in ICD–10 vary in this and other respects from the Centers for Disease Control and Prevention (CDC) criteria for CFS. Neuraesthenia and associated psychiatric morbidity in CDC-defined CFS are evaluated.

CFS subjects and controls were interviewed with the Schedule for the Clinical Assessment of Neuropsychiatry (SCAN). The computerised scoring program for SCAN (CATEG05) facilitates the assignment of operational definitions according to DSM–III–R and ICD–10. Subjects were re-interviewed with SCAN an average of 11 months later. No specific treatments or interventions were given during this period.

The majority of subjects fulfilled ICD–10 operational criteria for neuraesthenia and had two and a half times the rate of psychiatric morbidity as the healthy comparison group according to the CATEG05 Index of Definition (ID). Approximately 80% of subjects fulfilled both DSM–III–R and ICD–10 criteria for sleep disorders. There was a significant fall in the number of subjects fulfilling criteria for depression and anxiety disorders and a significant increase in the number of subjects with no diagnosis for DSM–III–R criteria over time. There were no significant changes over time for any diagnosis according to ICD–10 criteria or for overall levels of psychopathology as reflected in CATEG05 ID levels.

The ICD–10 ‘neuraesthenia’ definition identifies almost all subjects with CDC-defined CFS. Fifty per cent of CFS subjects also had depressive or anxiety disorders, some categories of which remit spontaneously over time.