The consumption of alcohol or another substance (drug) leads to health or social problems. This disorder is also called substance abuse. What defines drug dependency is the presence of a pattern to the use of the compulsive drug, which leads the person to consume larger quantities or for a longer period of time than initially the person intended.
The drug dependency syndrome is a set of behavioral, cognitive and physiological phenomena that are transformed into a repeated consumption of a substance and that, typically, includes the desire to consume the drug, the difficulties to control the consumption, and the persistence in the consumption despite the harmful consequences.