Substance use activates the dopamine process in the survival center much more powerfully than natural rewards like food or sex. When repeated it can hijack the brain, making it think that the substance is the most important thing for survival.
Over time, more and more of the substance is needed to activate the same level of reward, causing the brain’s circuits to become increasingly imbalanced--eroding a person’s self-control and ability to make sound decisions, while producing intense impulses to seek and use the substance.
This is what it means when scientists say that addiction is a brain disease.
The good news – SUDs are preventable and treatable, and brain scans show that once an individual is in recovery, brain tissue can get better.