This paper develops a theory of rational addiction, where rationality is defined as a consistent plan to maximize utility over time. The authors argue that strong addictions can be rational in the sense of involving forward-looking maximization with stable preferences. They introduce the concept of "adjacent complementarity," which describes the relationship between past and present consumption that leads to addictive behavior. The theory explains why rational addicts respond more to permanent changes in prices and why they often go on binges. It also suggests that anxiety and tensions can precipitate addiction. The paper analyzes the dynamics of consumption and the role of initial consumption capital in determining whether steady-state consumption levels are stable or unstable. It further explores how permanent changes in income and prices affect the long-run demand for addictive goods. The authors conclude that rational addiction can explain why severe addictions often require abrupt cessation, or "cold turkey," and why rational addicts respond more to permanent changes in prices.This paper develops a theory of rational addiction, where rationality is defined as a consistent plan to maximize utility over time. The authors argue that strong addictions can be rational in the sense of involving forward-looking maximization with stable preferences. They introduce the concept of "adjacent complementarity," which describes the relationship between past and present consumption that leads to addictive behavior. The theory explains why rational addicts respond more to permanent changes in prices and why they often go on binges. It also suggests that anxiety and tensions can precipitate addiction. The paper analyzes the dynamics of consumption and the role of initial consumption capital in determining whether steady-state consumption levels are stable or unstable. It further explores how permanent changes in income and prices affect the long-run demand for addictive goods. The authors conclude that rational addiction can explain why severe addictions often require abrupt cessation, or "cold turkey," and why rational addicts respond more to permanent changes in prices.