State where the user continues its use of the substance despite significant health, psychological, relational, familial or social problems. Dependence is a complex phenomenon which may have genetic components. Psychological dependence refers to the psychological symptoms associated with craving and physical dependence to tolerance and the adaptation of the organism to chronic use. Physical dependence starts when cells of the body can not function without a substance or drug. Physical dependence can happen with the chronic use of many drugs (including many prescription drugs).