Drugs are chemicals. When they reach the brain, they interfere with how your brain cells work.
Drugs affect the way that nerve cells send and receive messages. In recent decades, extensive scientific research has explored the nature of substance use disorder to gain a better understanding of addiction and how to treat it. We now know more about how drugs affect the brain and the biology of addiction.
The Brain’s Reward System
Most commonly abused drugs, including opiates, alcohol, nicotine, amphetamines, and cocaine, affect the brain’s reward system.
The reward system is a healthy part of how your brain works. When you do certain activities, such as exercising or socializing, your brain releases the chemical dopamine. Dopamine produces positive feelings and causes you to experience the activity as pleasurable. It also encourages you to do the activity again.
Drugs interfere with this process. When you take a drug, it floods your brain with dopamine, producing positive feelings or euphoria. The brain connects this with the drug and sends out signals for you to use it again.
Because drugs produce much more dopamine than the brain naturally releases, the brain’s response is also stronger. The urge to use the drug can be incredibly intense and difficult to resist.
Over time, the brain starts to release dopamine in response to cues in your environment that you associate with drugs. This may be a place you take drugs or friends you use with. These cues can trigger the urge to use a substance.