Lawrence Marshall, a distinguished consultant neurosurgeon, had a minor head injury in 1984 while skiing.1 He was unconscious at most for 15 seconds. Cognitive symptoms were immediately present but improved over the course of many months; his work was not affected. On the other hand some people, after a blow to the head of equivalent force, will be severely incapacitated with psychological symptoms lasting years. These diverse outcomes reflect the complexity of the interaction between physiological and psychological processes in the development of symptoms after head injury.2 Perhaps, therefore, a good starting point is …