Abstract
In this thesis all studies are related to the development of the treatment manual 'Cognitive Behaviour Therapy (CBT) for Chronic Fatigue Syndrome (CFS)'. After a study on the prevalence of CFS in the Netherlands, two studies on possible physiological processes underlying CFS are presented. In one study the role of hyperventilation is reported. The second study concerns the role of physical fitness. Although physiological evidence of hyperventilation in CFS was found, CFS patients with and without physiological hyperventilation did not differ in other aspects but hyperventilation. The second study showed that CFS patients and healthy controls did not differ in physical fitness. It is concluded that hyperventilation and physical fitness do not play a substantial perpetuating role in CFS. Although no evidence was found that physiological processes were involved in the perpetuation of CFS, many studies proved cognitive and behavioural factors to be important. Based on a model of perpetuating factors, a first cognitive behavioural treatment for CFS was developed. Two studies on this subject are presented: the first concerning the effect of cognitive behaviour group therapy (CBGT), the second of individual CBT. Regarding CBGT, studied in a wait list design, only a moderate effect on fatigue in favour of CBGT was found. Individual CBT for CFS was compared with two control conditions, guided support groups and the natural course. Individual CBT was significantly more effective than both control conditions for fatigue severity and for functional impairment. In a following study therapists' adherence and perceptions of the manual are investigated. As a result of these studies, the treatment manual CBT for CFS was regularly adapted. The last version, 'CBT for relatively active and for passive CFS patients', is described in the final chapter.
