Figure 2

Proposed model of the origin of sustained arousal in Chronic fatigue syndrome. Certain threats to homeostasis, such as long-lasting infections and psychosocial challenges, may elicit a prolonged arousal response, which does not, however, solve the initial problem (1). The mutual relation to cognitive processes results in negative stimulus and response outcome expectancies, creating a vicious circle (2). Certain genetic traits and aspects of personality may reinforce the arousal response further. This situation causes homeostatic instability in itself, establishing another vicious circle (3). In addition, the arousal response may eventually become associated with neutral events, such as moderate physical activity, through the process of classical conditioning (4). We propose that these mechanisms altogether elicit a state of sustained arousal (5).