Allostasis, originally conceptualized to explain persistent morbidity of arousal and autonomic function, can be defined simply as “stability through change” (Sterling and Eyer 1988). Allostasis is different from homeostasis. Allostasis involves a feed-forward mechanism rather than the negative feedback mechanisms of homeostasis. Allostasis involves a changed set point with continuous re-evaluation of need and continuous readjustment of all parameters toward new set points. The set point in question here is emotional state. An allostatic state can be defined as a state of chronic deviation of the reward system from its normal (homeostatic) operating level. Allostatic load has been defined as the “long-term cost of allostasis that accumulates over time and reflects the accumulation of damage that can lead to pathological states” (McEwen 2000). Although the concept of allostatic state has not received much attention, the argument here is that alcoholism reflects largely a movement to an allostatic state, often before sufficient pathology has ensued to produced allostatic load sufficient for physical pathology (Koob and Le Moal 2001).
