There are tools for measuring the level of dependence and addiction for different substances (like the severity of dependence scale.) You may also be intereste

There are tools for measuring the level of dependence and addiction for different substances (like the severity of dependence scale.) You may also be interested in studies on caffeine dependence, like: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3777290/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3777290/ > Numerous controlled laboratory investigations reviewed in this article show that caffeine produces behavioral and physiological effects similar to other drugs of dependence. Moreover, several recent clinical studies indicate that caffeine dependence is a clinically meaningful disorder that affects a nontrivial proportion of caffeine users.