Physical Dependence

Physical dependence occurs when a drug has been chronically used so often that the body has developed tolerance to the substance and the person suffers withdrawal symptoms when they stop using the drug. This differs from psychological dependence (where a person emotionally depends on a substance) in that the body actually 'needs' the drug in order to feel normal and avoid the adverse symptoms of withdrawal. The longer the person has been using the drug and greater amounts of the drug make physical dependence more likely and the withdrawal symptoms worse.