Drugs are chemicals. When you use a drug, it travels into your brain and changes how your brain cells work, and even affects how nerve cells send, receive, and process information.
Different drugs affect brain cells in different ways. There are at least two main ways drugs work on the brain.
Imitating the Brain’s Natural Chemical Messengers
Drugs like heroin and marijuana have structures that look and act like neurotransmitters that naturally occur in our brains. The receptors in our brains think that they are normal cells and lock onto them. They begin to send messages throughout the brain as a normal neurotransmitter would. However, the drug does not work exactly like a normal neurotransmitter. The messages they send are abnormal and cause damage to our brains and bodies.
Other drugs work by affecting how nerve cells release dopamine. Dopamine is a natural neurotransmitter that results in pleasurable feelings. Drugs like cocaine cause nerve cells to release too much dopamine or stop the cells from recycling dopamine in the usual way. It results in exaggerated messages in the brain, disrupting communication channels. This causes problems in your brain and body.
The ‘Reward’ System
Many drugs, such as cocaine and marijuana, affect the brain’s reward system.
The reward system is a natural and healthy part of how the brain works. When you eat chocolate or go for a run, your nerve cells release a small amount of dopamine. This is what makes the activity pleasurable. It also encourages you to do the activity again.
When you use a drug, it affects this system. It releases large amounts of dopamine in response to the drug, producing feelings of euphoria. The brain connects this feeling with the drug and sends out strong urges to use the drug again. These urges can be incredibly intense.
Over time, the brain also begins to release dopamine in response to cues it associates with the drug. This could include seeing someone you take drugs with or being in a place you usually take them, and these cues become ‘triggers’ that produce a sudden urge to use the substance.
Repeated drug use over a long time can lead to dramatic changes over large areas of the brain, and in some cases, these changes are irreversible. This is why addiction is viewed as a chronic illness.