Hydrocodone addiction occurs when the brain gets used to the increased levels of dopamine. Over time, as the brain adapts to the drug, tolerance develops, and the user needs more hydrocodone to achieve the same results as before. Higher doses of the drug can lead to dependence, meaning that the body requires the drug to function normally and will go through withdrawal if the drug is taken away. Once dependence develops, addiction may follow. Addiction involves a psychological dependence on the drug, such that the person has a hard time stopping the drug even if they want to and are aware of the negative consequences.