In terms of the neurobiological theories of the development of addiction through alcohol response adaptation, the findings in those progressing with alcohol problems provide initial support for the early stage of addiction in the allostasis model with heightened stimulation and reward sensitivity that did not diminish over time. Koob and colleagues have coined the later stage of addiction as “the dark side of addiction”(65) because it is characterized by development of reward insensitivity and drinking behaviors related to negative reinforcement. This type of alcohol adaptation was not observed in heavy drinkers progressing with AUD, and the majority of persons in this subgroup either maintaining heightened stimulation or increasing further at re-examination, with only 2 of 9 high AUD individuals showing a lessening of response. This could be due to several reasons: a 5-year re-examination interval in humans may not be sufficiently long to show later-stage changes in reward sensitivity, allostasis may only occur only in the most extreme alcoholics with significant withdrawal not selected for the sample due to ethical constraints, or the allostasis phenomena modeled in animal studies may not translate to the development of human AUD.
