Your brain is who you are. It’s what allows you to think, breathe, move, speak, and feel. It’s just 3 pounds of gray-and-white matter that rests in your skull, and it is your own personal “mission control.”

The brain is always working, even when you're sleeping. Information from your environment makes its way to the brain, which receives, processes, and integrates it so that you can survive and function under all sorts of changing circumstances and learn from experience. This information comes from both outside your body (like what your eyes see and skin feels) and inside (like your heart rate and body temperature).

The brain is made up of many parts that all work together as a team. Each of these different parts has a specific and important job to do. When drugs enter the brain, they interfere with its normal tasks and can eventually lead to changes in how well it works. Over time, drug use can lead to addiction, a devastating brain disease---when people can’t stop using drugs even when they really want to, and even after it causes terrible consequences to their health and other parts of their lives. (Learn more about the brain-body connection.)

Drugs affect mostly three areas of the brain:

• The brain stem is in charge of all the functions our body needs to stay alive—breathing, moving blood, and digesting food. It also links the brain with the spinal cord, which runs down the back and moves muscles and limbs. It also lets the brain know what’s happening to the body.
• The limbic system links together a bunch of brain structures that control our emotional responses, such as feeling pleasure when we eat chocolate or kiss someone we love. The good feelings motivate us to repeat the behavior, which can be good because things like eating and love are critical to our lives.
• The cerebral cortex is the mushroom-shaped outer part of the brain (the gray matter). In humans, it is so big that it makes up about three-fourths of the entire brain. It’s divided into four areas, called lobes, which control specific functions. Some areas process information from our senses, allowing us to see, feel, hear, and taste. The front part of the cortex, known as the frontal cortex or forebrain, is the thinking center. It powers our ability to think, plan, solve problems, and make decisions.

The brain is a complex communications network of billions of neurons, neurotransmitters, and receptors. Networks of neurons pass messages back and forth thousands of times a minute within the brain, spinal column, and nerves. These nerve networks control everything we feel, think, and do. For example, when you want to go up the stairs, this message system will tell you to lift your foot onto the first step and so on. Understanding these networks helps scientists learn how drugs affect the brain. The networks are made up of:

• Neurons
  Your brain contains about 100 billion neurons—nerve cells that work nonstop to send and receive messages. Within a neuron, messages travel from the cell body down a nerve fiber called an axon in the form of electrical impulses. From there, the message is sent to other neurons.
• Neurotransmitters—The Brain's Chemical Messengers
  To help those messages travel from one neuron to another, the brain creates chemical messengers called neurotransmitters. Branches of the axon, called axon terminals, release neurotransmitters into the space between two nerve cells, called a synapse. The axon terminal is like the bus or train terminal - a transportation hub of activity.
• Receptors—The Brain's Chemical Receivers
  As the neurotransmitter approaches the nearby neuron, it attaches to a special site on that neuron called a receptor. A neurotransmitter and its receptor operate like a key and lock--- a very specific mechanism makes sure that each receptor will forward the right message only after interacting with the right kind of neurotransmitter.
• Transporters—The Brain’s Chemical Recyclers
  Once neurotransmitters do their job, they are pulled back into their original neuron by transporters. This recycling process shuts off the signal between the neurons.

Drugs are chemicals. When someone puts these chemicals into their body, either by smoking, injecting, inhaling, or eating them, they tap into the brain’s communication system and tamper with the way nerve cells normally send, receive, and process information. Different drugs—because of their chemical structures—work differently. We know there are at least two ways drugs work in the brain:

• Imitating the brain’s natural chemical messengers
• Overstimulating the “reward circuit” of the brain

Some drugs, like marijuana and heroin, have chemical structures that mimic a neurotransmitter that naturally occurs in our bodies. In fact, these drugs can “fool” our receptors, lock onto them, and activate the nerve cells. However, they don't work the same way as a natural neurotransmitter, and the neurons wind up sending abnormal messages through the brain, which can cause problems both for our brains and our bodies.

Other drugs, such as cocaine and methamphetamine, cause nerve cells to release too much dopamine, a natural neurotransmitter, or prevent the normal recycling of dopamine. This leads to exaggerated messages in the brain, causing problems with communication channels. It’s like the difference between someone whispering in your ear versus someone shouting in a microphone.

The “High” From Drugs/Pleasure Effect

Scientists used to assume that the rush of dopamine alone caused the feeling of euphoria (happiness) during drug use, but they now know it is more complicated than that. Many drugs—nicotine, cocaine, marijuana, and others—affect the brain’s “reward” circuit, which is part of the limbic system. Normally, the reward circuit responds to healthy, pleasurable activities by releasing the neurotransmitter dopamine, which teaches other parts of the brain to repeat those activities. Drugs take control of this system, releasing large amounts of dopamine—first in response to the drug but later mainly in response to other cues associated with the drug—like being with people you used drugs with, or being in places where you used drugs. The brain remembers this feeling and sends out an intense motivation to seek and use the drug again. So dopamine does not cause the rush of feelings; instead it reinforces the desire to use drugs.

The Repeat Effect

Our brains are wired to make sure we will repeat survival activities, like eating, by connecting those activities with feeling good. Whenever this reward circuit is kick-started, the brain notes that something important is happening that needs to be remembered, and teaches us to do it again and again, without thinking about it. Because drugs come in and “hijack” the same circuit, people learn to use drugs in the same way.

After repeated drug use, the brain starts to adjust to the surges of dopamine. Neurons may begin to reduce the number of dopamine receptors or simply make less dopamine. The result is less dopamine signaling in the brain—like turning down the volume on the dopamine signal. Because some drugs are toxic, some neurons also may die.

As a result, the ability to feel pleasure is reduced. The person feels flat, lifeless, and depressed, and is unable to enjoy things that once brought pleasure. Dopamine encourages the brain to repeat the pleasurable activity of drug taking to feel good again. Now the person needs drugs just to feel normal, an effect known as tolerance.

Watch our video Why Are Drugs So Hard To Quit? to learn more.

Long-Term Effects

Drug use can eventually lead to dramatic changes in neurons and brain circuits. These changes can stay even after the person has stopped taking drugs. This is more likely to happen when a drug is taken over and over again.

Addiction is a chronic brain disease that causes a person to take drugs or alcohol repeatedly, despite the harm they cause. The first time a person uses drugs, it’s usually a free choice. However, repeated drug use can change the brain, driving a person to seek out and use drugs over and over, despite negative effects such as stealing, losing friends, family problems, or other physical or mental problems brought on by drug use. This is addiction.

Although we know what happens to the brain when someone becomes addicted, we can’t predict how many times a person must use a drug before becoming addicted. A combination of factors related to your genes, environment, and your personal development increases the chance that taking drugs will lead to addiction. These include:

• Home and family. Parents or older family members who use alcohol or drugs, or who are involved in criminal behavior, can increase a young person’s risk for developing a drug problem.

• Peers and school. Friends and acquaintances who use drugs can sway young people to try drugs for the first time. Academic failure or poor social skills can also put a person at risk for drug use.

• Early use. Although taking drugs at any age can lead to addiction, research shows that the earlier a person begins to use drugs, the more likely they are to progress to more serious use. This may reflect the harmful effect that drugs can have on the developing brain. It also may be the result of early biological and social factors, such as genetics, mental illness, unstable family relationships, and exposure to physical or sexual abuse. Still, the fact remains that early drug use is a strong indicator of problems ahead—among them, substance use and addiction.

• Method of use. Smoking a drug or injecting it into a vein increases its addictive potential. Both smoked and injected drugs enter the brain within seconds, producing a powerful rush of pleasure. However, this intense "high" can fade within a few minutes, and the person no longer feels good. Scientists believe that this low feeling drives people to repeat drug use in an attempt to recapture the high pleasurable state.

Yes, deaths from drug overdose have been rising steadily over the last decade, largely due to increases in misuse of opioids.

In addition, death can occur from the long-term effects of drugs. For example, long term use of tobacco products can cause cancer, which may result in death.

Yes, there are treatments to help manage addiction, but there is no cure. It is considered a chronic disease, meaning it lasts a long time and needs to be managed with regular treatment. If people follow treatment plans, they can go for many years leading healthy lives. It can be similar to other chronic conditions that people learn to manage, like diabetes or heart disease. Scientific research has shown that 13 basic principles are the foundation for effective drug addiction treatment. Find out more in Principles of Adolescent Substance Use Disorder Treatment: A Research-Based Guide.

Types of Treatment

Treatment will vary for each person, depending on the type of drugs used and the person’s specific circumstances. Generally, there are two types of treatment for drug addiction:

• Behavior change--- helping people learn to change behaviors that trigger drug use
• Medications--- helping people manage cravings for some drugs, such as tobacco, alcohol, heroin, or other opioids

Length of Treatment

Most people who have become addicted to drugs need long term treatment and, many times, repeated treatments—much like a person who has asthma needs to constantly watch the effects of medication and exercise. Even when someone relapses and begins using drugs again, they should not give up hope--- they might need to change to a different treatment plan. In fact, setbacks are likely. Even people with diabetes may go off their diet or miss an insulin injection, and their symptoms will recur—that’s a cue to get back on track, not to view treatment as a failure.

Motivation for Treatment

Most people go into drug treatment either because a court ordered them to do so or because loved ones wanted them to seek treatment. Many people are tired of addiction and its problems, and chose to go into treatment. Others are ordered into treatment by a judge or under pressure from family members.

The signs listed below may suggest a developing problem, which you should discuss with an adult you trust:

• hanging out with different friends
• not caring about your appearance
• getting worse grades in school
• missing classes or skipping school
• losing interest in your favorite activities
• getting in trouble in school or with the law
• having different eating or sleeping habits
• having more problems with family members and friends

Questions to Ask: Do You Have a Problem? 

Answering yes to any of the following questions may indicate a problem:

1. Have you ever ridden in a car driven by someone (including yourself) who had been using alcohol or drugs?
2. Do you ever use alcohol or drugs to relax, to feel better about yourself, or to fit in?
3. Do you ever use alcohol or drugs when you are alone?
4. Do you ever forget things you did while using alcohol or drugs?
5. Do family or friends ever tell you to cut down on your use of alcohol or drugs?
6. Have you ever gotten into trouble while you were using alcohol or drugs?