The brains complex circuitry systems change, often   permanently when anyone who has abused drugs or alcohol regularly for a period of time. They  will exhibit physical changes in their brain, with pathways associated with emotional regulation, decision making, impulse control and pleasure all unfavourably altered.

Addiction also affects homeostatic balance, with chronic overstimulation of the brain (like that which occurs in addiction) forcing the brain to make adjustments and create a new balance point, known as allostasis.