|Abstract:||Relapse is the chief problem of drug addiction where a successfully abstinent patient returns to seemingly extinct manners of drug consumption. While various parameters were identified as affecting relapse, the general dynamics of drug consumption is yet to be understood. We introduce a model that describes addiction focusing on a single state- value factor, mediated in the Nucleus Accumbence (NAC) that subsequently affects the likelihood of drug consumption. Various parameters influence and change the state-value factor. These parameters represent afferent extracellular neurotransmitter levels affecting the cortico-striatal loops that determine behavior. This provides an interesting combination where the dynamics described by the model can describe the dynamic of drug consumption, including consumption, abstinence and relapse, and the model’s details are based on extracellular neurotransmitter levels. Thus, our model can provide not only a more complete description of addiction as a dynamical decision biased process but may also turn useful for studying and evaluating possible treatments on individual basis.