It is well known and often said that use of addictive substances [G] is highly destructive to individuals and to society as a whole. Substance use [G], legal and illegal, is widespread in most populations. Individuals who use substances frequently or heavily can lose control of their substance use behaviours, resulting in substance use disorders [G] (SUDs) — substance use that is no longer under the person’s full control, often because of physiological substance dependence [G]. Over the years, there has been considerable debate over the extent to which SUDs should be considered habits or behaviours on the one hand, or medical illnesses on the other. A rather dim view of these behaviours has been taken by some under the assumption that they can be controlled with sufficient effort; this view has influenced the stigma our society attaches to SUDs. The biological data, including the genetic data, tell a different story though: what begins as habit or volitional behaviour becomes a genetically influenced brain disease where substance abuse [G] creates a continuing need for the substance in the affected individual.
