Addicted people lose control over their actions. They crave and seek drugs, alcohol, or other substances regardless of the cost, even at the risk of harming friendships, harming family, or losing their job. What is it about addiction that causes people to behave in such destructive ways? And why is it so difficult to quit smoking? Substance abuse is a pattern of compulsive substance use characterized by significant recurring adverse social, occupational, legal, or interpersonal consequences, such as repeated absences from work or school, arrests, and marital difficulties. Substance use disorders are the result of changes in the brain that can occur with repeated use of alcohol or drugs.
The most serious expression of the disorder, addiction, is associated with changes in the function of the brain circuits involved in pleasure (the reward system), learning, stress, decision-making and self-control.