SIR—Adam Zeman (Sept 13, p 795) is to be congratulated on his excellent discussion of the concept of persistent vegetative state (PVS). As he points out, this concept is based on a particular model of consciousness and wakefulness that has certain shortcomings. The shortcomings are well illustrated by two consecutive sentences in his conclusion: “Consciousness [or awareness], in all its aspects, is a matter of degree”, and “The vegetative state [is] a condition of wakefulness without awareness”. The first correctly identifies awareness as a continuum rather than a quality that is either present or absent. The second should therefore define PVS as a state of wakefulness without a set amount of awareness. This definition makes the concept less superficially attractive (and begs the question how awareness is measured and how much is allowed in 5-HT2A receptor gene polymorphisms, anorexia nervosa, and obesity