Many drugs affect the brain’s “reward” circuit in the brain. Normally, this part of the brain responds to healthy, pleasurable activities by releasing the neurotransmitter dopamine, which teaches the brain to repeat those activities After repeated drug use, the brain starts to adjust to the surges of dopamine, and responds by making less of it. The result is less dopamine signaling in the brain—like turning down the volume on the reward signal. This means that the person starts to find natural rewards – like food, relationships, or sex -- less pleasurable, one of the signs of addiction.
Some drugs are toxic to the brain and cause some brain cells to die. Drug use can eventually lead to dramatic changes in neurons (brain cells) and brain circuits, which result in addiction. Learn more at http://www.scholastic.com/drugs-and-your-body/brain.htm, and on this link to find out how drugs affect your body: http://www.scholastic.com/drugs-and-your-body/.