How Drugs and Alcohol Affect the Brain?

When you feel that rush, that high that comes from drinking alcohol or using a drug, you just know it’s affecting your brain. And you want that effect or you wouldn’t do it. But have you ever wondered how that happens? How do drugs affect the brain? You might be surprised that it’s not that complicated. However, it may cause complications in the future.

It should be no shock to learn that your brain is the most complex organ in your body. That 3-pound mass of gray and white matter is in control of all of your activities. It is necessary to drive a car, to create art, to enjoy a meal, and to breathe, along with all of your body’s basic functions. So what is your brain? It’s you. It’s everything that you think and feel. It’s everything that you are.

How Does Your Brain Work?

You can compare your brain to a very complex computer. But the brain uses billions of cells called neurons instead of circuits on silicon chips. The neurons in the brain are organized into circuits and networks and each neuron acts as a switch that controls the flow of information. If a neuron gets enough signals from other neurons on the circuit, it sends off its own signal to the other neurons.

Neurotransmitters: Chemical Messengers

To send a message, this is the pattern:

  1. A neuron releases a neurotransmitter into the gap between it and the next cell.
  2. The neurotransmitter crosses the gap and attaches to the receptors on the next neuron, similar to a key into a lock.
  3. This “unlocking” causes changes in the receiving cell.
  4. Then, other molecules called transporters recycle the neurotransmitters by bringing them back to the neuron that sent them.
  5. This shuts off the signal between the neurons.

How This Works in Your Brain

How do drugs affect the brain? Well, When you use drugs or alcohol, it interferes with the way your brain’s neurons send, receive, and process the signals from the neurotransmitters. Thus, the pleasure of high-produced drugs likely involves surges of chemical signaling compounds (including the body’s natural opioids) and other neurotransmitters in parts of the reward circuit.

When a person uses certain drugs, the substances cause surges of these neurotransmitters. The surges are far greater than the smaller bursts that are naturally produced in response to healthy rewards like eating, sex, playing music, or social interaction.

Dopamine: The Reward Messenger

Scientists used to think that the surge of dopamine produced by the drugs caused the euphoria directly. But now, they believe that dopamine has more to do with influencing us to repeat pleasurable activities than by causing the pleasure directly. The sensation of pleasure is how a healthy brain recognizes and reinforces helpful behaviors such as eating, socializing, and sex.

Your brain is wired to increase the chances that you will repeat pleasant actions. The neurotransmitter dopamine is key to this. When the reward circuit is activated by a healthy, pleasurable experience, a rush of dopamine signals to your brain that something needs to be remembered. The signal causes changes in your neural connections that make it easier to repeat the activity over and over without thinking about it. Thus, the formation of habits.

The same way drugs produce excessive euphoria, they also produce large surges of dopamine. This strongly reinforces the connection between using the drug, the pleasure that results, and all the outside prompts (or triggers) associated with the experience. Therefore, large surges of dopamine teach the brain to choose drugs at the expense of other healthier activities.

Cues to Use

Cues in your normal daily routine or surroundings can become linked with drug use because of the changes to the reward circuit. These triggers can cause uncontrollable cravings even if the drug is not available or if you haven’t used drugs in years. A drug-free person can experience cravings when returning to a place where they used to use drugs many years before.

Why Drugs are More Addictive Than Natural Rewards

To your brain, the difference between normal rewards and drug-induced rewards is like the difference between a rainstorm and a hurricane. Similar to turning down the volume on a radio that is too loud, the brain of someone on drugs adjusts to the volume by producing fewer neurotransmitters in the reward circuit which reduces the number of receptors that can receive the reward message. As a result, the ability to feel pleasure from naturally rewarding activities is reduced.

Eventually, a person who misuses drugs will feel this cycle:

  • Lack of motivation
  • Lifelessness and/or depression
  • Inability to enjoy things that used to be pleasurable.
  • Desire to keep taking drugs to experience even a normal feeling of pleasure.

Ultimately, this individual will typically need to use larger amounts of the drug to end up with the usual pleasant sensations. He has built a tolerance to the drug. Tolerance leads to dependence which leads to addiction.

Endorphins, Heroin, and Your Brain

As soon as heroin enters the brain, it is changed into morphine and quickly attaches to the opioid receptors of the brain. Opioid receptors are neurons in the pain circuit of the brain. (Remember the circuits?) The sensation of pleasure, the rush, is caused by the amount of drug is taken and how fast it attaches to the receptors.

Morphine has a chemical structure similar to endorphins, another neurotransmitter that is naturally present in the brain. Although they are both neurotransmitters, endorphins are different from dopamine. Generally speaking, dopamine creates happiness after an individual has accomplished something. On the other hand, endorphins act to relieve pain which could also play a part in motivation and a feeling of pleasure. Therefore serving as a reward.

Heroin can activate neurons because their chemical makeup can imitate that of a natural neurotransmitter in the body. This is how the drug attaches to and activates the neurons. However, they aren’t able to activate the neurons the same way as the natural neurotransmitter and they cause abnormal messages to be sent through the network.

Long-Term Effects

Over time, the use of heroin and other opioids changes the physical structure and normal functions of the brain. It creates unevenness in neuron and hormone systems that aren’t easy to reverse. Studies have shown deterioration of the brain’s white matter which may affect:

  • The ability to control behavior
  • The ability to control reactions to stressful situations
  • Increased tolerance:
    • The need for more of the drug to produce the same results
    • Increase in physical dependence
    • Withdrawal symptoms if use is reduced or stopped suddenly

In some cases, the addict loses the euphoric effect. Heroin is then used simply as a way to relieve the uncomfortable and unpleasant withdrawal symptoms.


Although alcohol is absorbed throughout your whole body, it takes a particular toll on your brain. Once again, we see a substance interfering with the brain’s communication pathways and affecting how your brain process information.

Effects of Alcohol Consumption by Stages

  • Euphoria. When you first take a drink of alcohol, it increases the release of your favorite reward, dopamine. You feel relaxed with pleasant sensations and maybe some minor impairment of reasoning and memory.
  • Depression, memory loss, and confusion. After the blood alcohol level reaches past 0.0r blood alcohol content (BAC), your blood and body tissue absorbs the extra alcohol and your euphoria turns to depression.
  • Excitement. At this point, with a BAC from about 0.09 to 0.25 you are legally intoxicated. Several affected areas in your brain are responsible for blurred vision, slurred speech, and hearing, and lack of control of motor skills, and slower reaction time.
  • Confusion. At a BAC of 0.18 to 0.3 you are experiencing daze and disorientation. Coordination is affected. Blackouts, or the loss of consciousness or memory, are also likely. This is due to the area of the brain responsible for making new memories not functioning properly.


  • Stupor. If you get to a BAC of 0.25 to 0.40, alcohol poisoning may occur. At this time all physical, mental, and sensory capabilities are seriously defective.
  • Coma. A BAC of 0.35 carries the possibility of going into a coma because of weakened respiration and circulation, motor responses, and reflexes.
  • Death. A BAC over 0.45 may result in death from alcohol poisoning or a failure in the brain to control all of the body’s essential physical functions.

Lasting Damage

Continuous abuse of alcohol can cause lasting damage to your brain. It can lead to mental health problems such as depression and anxiety. Alcohol use disorder (AUD) can also lead to Wernicke-Korsakoff syndrome which features amnesia, extreme confusion, and visual disturbances.

Drinking alcohol can result in direct damage to the body’s tissues and indirect stress on your body. Fortunately, most mental impairment can be reversed or improved within a year of abstinence.

Cocaine and Amphetamines

Cocaine and amphetamines also increase the levels of our natural reward messenger, dopamine. As explained earlier, dopamine would normally recycle back to the cell that released it, shutting off the signal between the neurons. Using cocaine and other stimulants prevents the recycling event.

As a result, large amounts build up in the space between the nerve cells (neurons) blocking their normal communication. The abundance of dopamine in the reward circuit greatly reinforces drug-using behavior because the reward circuit eventually adjusts to the excess dopamine and becomes less sensitive to it. This begins the cycle of using stronger and/or more frequent doses known as tolerance. Which leads to dependence and then to addiction.

Long-term effects

  • Paranoia
  • Malnutrition
  • Irritability and restlessness
  • Movement disorders including Parkinson’s disease
  • Auditory hallucinations—hearing sounds that aren’t real


There is evidence from several studies that marijuana exposure during development can cause long-term or even permanent injury to the brain. This is especially possible when use starts in adolescence and continues to constant use in adulthood. Animal studies showed unusually high levels in the cannabinoid receptors in an animal brain.

THC, the active ingredient in marijuana is mildly hallucinogenic and probably interacts with several chemical pathways. Furthermore, memory damage from marijuana use happens because THC changes how the hippocampus (the area in the brain responsible for memory formation) processes information.

ABCD Study

Unfortunately, it’s difficult to make definite conclusions about the long-term effects of marijuana use on the human brain because the study participants tended to use multiple substances. Likewise, there is often little information about the participants’ health or mental functions before the study. The National Institutes of Health (NIH) is funding the Adolescent Brain Cognitive Development (ABCD) study This ABCD study will follow a large number of young Americans from late childhood (before drug use) to early adulthood.

Real Rewards Through Treatment

Ultimately, how do drugs affect the brain? The general answer is in numerous different ways. Thus, you can no doubt now see why addiction is considered a brain disease. It is a chronic disease like diabetes or hypertension and it can be treated. If you or someone close to you is struggling with an addiction, we can get you on the way to recovery at Florida Center for Recovery. Our experienced, professional staff has one job. Their duty is only to care for you or your loved one and help you through detox, therapy, and ongoing treatment. Contact us now. These issues are too serious to wait, or worse, ignore.