Sensitization is conceptually related to cognitive bias in experimental psychopathology, and they share the basic mechanism of neuronal sensitization. Every strongly relevant individual concern, like fears, can yield cognitive bias or "cognitive-emotional sensitization". It might also be present for bodily and environmental information related to illness, and could be an etiological factor in medically unexplained complaints. Physiological and cognitive sensitization are theoretically compared. There is evidence for cognitive-emotional sensitization in some medically unexplained somatic complaints, and negative affect is suggested as a catalyst. Prolonged cognitive-emotional sensitization ("perseverative negative cognition" or worry, rumination) might even have demonstrable somatic pathological effects. It is concluded that sensitization may be organized at different levels, both in the organism and in the larger living system within which the organism is subsumed. This view might not only help to clarify medically unexplained pain syndromes, but virtually every subjective complaint, both with and without recognized physiopathology.