How Do Drugs Affect the Brain?

Addiction and substance use can affect the brain on many levels.  The chemicals in different drugs from nicotine, heroin, and alcohol will enter your bloodstream and affect you in different ways. Continue reading to learn more about drugs and their affect on the brain. 

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Drugs can have a serious impact on the body. In fact, drug abuse and addiction can affect almost every system in an individual, from mood, judgment, decision-making, learning, and memory. Even more, drugs can lead to serious health problems like cancer, heart disease, lung disease, and more.

Drugs can affect the body when used in high doses, after prolonged use, and sometimes after just one use. Read on to learn more about the relationship between drugs, the brain, and how it affects individuals who abuse substances.

How Do Drugs Work in the Brain?

Drugs are substances that change the way the body and mind function. Drugs interfere with the way neurons send, receive, and process signals via neurotransmitters. It’s important to note that drugs come from various sources, including plants, processed plant products, and synthetic chemicals.

There are a variety of ways that drugs can be taken, including:

  • Swallowing tablets or liquids
  • Breathing them into your lungs
  • Snorting in the nose
  • Injecting
  • Through the skin
  • Rectally or vaginally as a suppository
Types of Drugs

Drugs can be broken down into a variety of categories, including:

  • Central Nervous System Depressants: CNS depressants are a type of drug that slows down the brain and the body. An example of this type of depressant includes alcohol and anti-anxiety tranquilizers.
  • CNS Stimulants: These stimulants accelerate the heart rate and elevate a person’s blood pressure. Essentially, a CNS stimulant works to over-stimulate the body. Examples of these stimulants include cocaine, amphetamine, and methamphetamine.
  • Hallucinogens: Taking hallucinogens causes individuals to perceive things differently than they actually are. An example of a hallucinogen is an LSD, MDMA, and peyote.
  • Dissociative Anesthetics: This includes drugs that inhibit pain by cutting off the way the brain perceives it. PCP and dextromethorphan are two examples of dissociative anesthetic.
  • Inhalants: This includes a wide selection of breathable substances that produce results that alter the mind. Common examples of inhalants include Toluene, plastic cement, paint, and gasoline.
  • Cannabis: Also known as marijuana, the active ingredient in cannabis is delta-9 tetrahydrocannabinol or THC.
  • Narcotic Analgesics: This drug relieves pain, induces euphoria, and creates mood changes in the individual. Some examples of narcotics include opium, codeine, heroin, and morphine.
How Does the Brain Work?

The brain is a complex system with many working parts. Ultimately, the brain sends and receives chemical and electrical signals throughout the body. It’s important to note that different signals control different processes in the body and the brain works to interpret each one of them.

For instance, some signals will make an individual feel tired, while others signals can make you feel pain. Some signals are kept within the brain. While some signals travel through the spine and the body’s various networks of nerves to extremities.

Drugs and the Brain

Engaging in drugs, whether continuously or on a one-time basis, has a certain effect on the brain. When a person decides to engage in drugs, they will begin to interfere with the way in which the neurons work in the brain. Drugs influence the way neurons send, receive, and process the signals sent by the neurotransmitters.

Certain drugs, such as heroin and marijuana, can activate neurons because their chemical structure mimics a neurotransmitter in the body. As a result, the drugs are able to attach to the active neurons in the body.

However, these substances won’t activate the neurons in the same way that natural neurotransmitters do. This leads to abnormal messages being sent throughout the network and affects how the brain responds.

Other drugs like cocaine and amphetamines can lead to the neurons releasing abnormally large amounts of natural neurotransmitters. These drugs may also prevent the normal recycling of brain chemicals by interfering with transporters. As a result, this disrupts the normal communication between the neurons.

What Part of the Brain is Affected With Drugs?

Research has shown that there are specific parts of the brain that are affected by drug use. These areas include the basal ganglia, the extended amygdala, and the prefrontal cortex. Here is a closer look at how these parts of the brain are affected by drugs.

Basal Ganglia

One part of the brain that is affected by drugs is the basal ganglia. The basal ganglia refer to a group of subcortical nuclei within the brain. It is primarily responsible for motor control and is also responsible for other roles.

These roles include motor learning, executive functions, emotional behavior, and risk and reinforcement. Additionally, the basal ganglia also deal with addictive behaviors and habit formation.

The basal ganglia are located at the base of the cerebrum. The disruption of the basal ganglia network can lead to a variety of disorders related to movements. Examples include Parkinson’s and Huntington’s Disease.

While everyone will be affected by drugs in different ways, all addictive drugs produce dopamine, a pleasurable surge of the neurotransmitter, to the basal ganglia. However, with repeated use of drugs, the basal ganglia will adapt to the dopamine. This will reduce its sensitivity and make it more difficult to gain pleasure from any other experience aside from the drug.

Extended Amygdala

Another important part of the brain is the extended amygdala. This region of the brain is responsible for a variety of feelings, such as anxiety, irritability, and unease. Individuals who have withdrawal from a particular drug will experience these same symptoms after the drug fades. This experience motivates the person to seek out the drug again.

It’s important to note that the extended amygdala becomes sensitive as the individual continues to use the drug. When a person engages in substance abuse, they eventually use the drug in order to relieve discomfort rather than to experience a high.

Prefrontal Cortex

The prefrontal cortex plays an important role in cognitive control functions and dopamine. The prefrontal cortex is located in the cerebral cortex and covers the front part of the frontal lobe. This part of the brain is responsible for complex cognitive behavior, personality expression, decision making, and social behavior.

Out of all parts of the brain, the prefrontal cortex is the last to mature, which particularly makes teens more vulnerable. As the balance within the brain shifts a person dealing with substance abuse will compulsively seek their drug of choice. They will typically experience reduced impulse control.

How Do Drugs Work in the Body?

No matter what type of drug a person engages in, the substance will take a certain pathway through the body. It’s important to note that substances can enter the body in a variety of ways. In fact, drugs can be snorted, smoked, injected, swallowed, or applied to the skin. Some substances, such as marijuana, can be eaten.

How the drug is ingested, and other factors will determine how quickly the drug will take an effect. Once a person takes a drug, it will be absorbed into the bloodstream. The circulatory system will then distribute the drug throughout the body. Next, the body metabolizes it, and then the drugs and their metabolites are excreted.

Here is a closer look at how drugs work in the body:


This refers to the drug’s process when it is administered and then enters the person’s bloodstream. With that said, the administration process can happen in a variety of ways, including:

  • Oral intake: Oral intake can occur in various ways, including swallowing pills, drinking a liquid, and eating. When someone ingests a drug orally, the substance’s absorption will typically happen in the small intestine. Next, the drug will move to the liver and head back to the bloodstream to reach its destination.
  • IV injection: Another way that drugs are administered is through IV injection. This is when the substance has been delivered through the bloodstream. It’s important to note that when a drug is administered via IV injection, it is 100% absorbed. Additionally, the effects of drugs taken through injection are absorbed quickly, but will also wear off quickly.
    Subcutaneous injection: This type of administration occurs when there is an injection in the fatty tissue underneath the skin. This allows the substance to move to the capillaries or lymphatic vessels and finally into the bloodstream.
  • Snorting: When a drug is snorted, the substance is absorbed through the nasal tissues and into the bloodstream. Those who snort drugs will notice that the effects of it will come on a lot more quickly than an oral administration. However, the effects will not take place as quickly as smoking or injecting it.
  • Inhalation: Those who inhale drugs will typically vape or smoke the substance. The vape or smoke goes into the lungs and then enters the bloodstream as quickly as an injection would. Inhalation results in an extreme high, but it will wear off quickly as an injection does.
  • Transdermal: This method of administration is not all that common. When drugs are administered using this route, a patch is applied to the skin. Which then allows the substance to be absorbed into the bloodstream and then circulates throughout the body.


Once a drug has officially been absorbed, the substance is then carried through the body. The substance moves from the bloodstream to the tissue and intracellular fluids. It then binds to receptors.

One thing that’s important to note is that distribution is reversible. In fact, the molecules that are released from the receptors have an opportunity to travel back to the bloodstream.

When an individual experiences side effects from a drug, it typically happens during the distribution process. This makes distribution partially responsible for unintended side effects of drug use. Another potential effect that can occur during distribution is the damage of an organ(s) as the drug is being carried through the body.

Before a drug reaches the central nervous system, it must pass the blood-brain barrier. However, many drugs are not able to pass this barrier. When drugs don’t cross the barrier, a person will experience a variety of effects. One common effect is a sense of euphoria that is associated with illicit drugs and the nonmedical use of some medications.

When drugs do pass the blood-brain barrier repeatedly, it will become more difficult for a person to feel pleasure from natural rewards. This disruption may lead to compulsive drug use.

Additionally, drugs that continuously pass the blood-brain barrier can lead to issues with executive functioning, such as planning, making decisions, and problem-solving.

It’s important to note that some research suggests that certain drugs like cocaine and methamphetamine can change the blood-brain barriers function over time. More specifically, continued use of drugs can lead to the permeability of the blood-brain barrier, decreasing its effectiveness. As a result, it can become easier for viruses and bacteria to enter the brain.


Once a drug has been distributed, the next step is metabolization. This is the step where the drug will be broken down and will take place mainly in the liver, the body’s largest intestinal organ. Though my metabolization occurs in the liver, some metabolism can also occur in other organs, such as the kidneys, GI tract, and lungs.

During metabolism, enzymes break down the drug molecules, creating metabolites. It’s important to note that the process of enzymatic breakdown can make it easier for drugs to be excreted, which is the final phase of metabolism.


The last stage of the process is excretion. In this stage, the drugs along with their metabolites, leave the body.

They typically exit through the urine or feces. It’s possible for drugs to be secreted through other places as well, such as sweat, saliva, breast milk, or exhaled air.

How Do Drugs Affect the Nervous System?

To understand how drugs affect the nervous system, it’s important to understand the various parts of the nervous system. With that said, the nervous system consists of three parts. This includes the brain, spinal cord, and the nerves located outside of the brain and spinal cord.

Essentially, these three parts of the nervous system can be broken into two major components: the central and peripheral nervous systems.

Central Nervous System

This includes the brain and the spinal cord. 

Peripheral Nervous System

This includes a collection of nerves outside of the brain and the spinal cord. The peripheral nervous system functions to connect the central nervous system to the rest of the body. The system can be divided into two subdivisions:

  • The somatosensory nervous system: This section of the peripheral nervous system is considered to be under the voluntary control of the individual. It also includes nerves that are attached to the skeletal muscles.
  • The autonomic nervous system: This section of the peripheral nervous system is not considered to be under voluntary control.

The autonomic nervous system is further broken down into two subdivisions. Including the sympathetic nervous system which stimulates functions in the body. And the parasympathetic nervous system which slows down functions in the body.

The nervous system is mainly controlled by the brain. The spinal cord is used to transmit messages from the brain to different areas of the body. While also receiving information from different parts of the body. The nervous system has three functions: collecting information from the environment, interpreting the sensory information, and responding to the sensory inputs.

How Do Drugs Affect the Nervous System?

Chronic drug use can affect the central nervous system in a variety of ways. Some ways it can affect the nervous system can include:

Alterations in the reward pathways

The “reward pathways” are used to describe a specific neural pathway involved with the reinforcement and repetition of certain behaviors that lead to positive results. When a person engages in a pleasurable act, such as taking drugs, this part of the brain becomes activated. Additionally, it can potentially lead to structural changes in this particular brain area.

Changes in the brain pathways

When a person engages in drugs, there are typically compensatory changes that affect the brain. This is because when neurotransmitters, such as dopamine, are constantly released in significant amounts, the nervous system will make alterations to accommodate the new increase.

Increased Risk of Brain Disease or Brain Damage

Chronic drug use can lead to a condition called encephalopathy. This condition is used to describe brain damage or disease of the brain. Encephalopathy can lead to a change in a person’s cognition, emotional, and mental state.

Structural Changes in the Neurons

Chronic use of drugs and alcohol can lead to changes in the structure of the nerves in the brain, neurons, and certain supporting structures.

Get Treated With SoCal Sunrise Today

Drugs are substances that can seriously impact an individual’s health. Substance use disorder can have a profound impact on the brain and behavior. In many cases, the person struggling will also have mental health issues. The human brain is a complex network that can be deeply impacted by the effects of drug use.

Here at Southern California Sunrise Recovery Center, our goal is to heal the body, mind, and soul through rehab services, holistic therapy, and medical detox.

We offer a mix of scientifically proven addiction treatment with techniques paired with holistic methods to help individuals get on the path of recovery. Contact us today to learn more about our comprehensive services.

References & Resources

  1. U.S. Department of Health and Human Services. (2022, March 22). Drugs and the Brain. National Institutes of Health. Retrieved from

  2. Hudgins, J. D., Porter, J. J., Monuteaux, M. C., & Bourgeois, F. T. (2019, November 5). Prescription opioid use and misuse among adolescents and young adults in the United States: A national survey study. PLoS medicine. Retrieved June 29, 2022, from

  3. Lanciego, J. L., Luquin, N., & Obeso, J. A. (2012, December 1). Functional neuroanatomy of the basal ganglia. Cold Spring Harbor perspectives in medicine. Retrieved from

  4. Dopamine: What it is, Function & Symptoms. Cleveland Clinic. (n.d.). Retrieved from

  5. Giardino, W. J., & Pomrenze, M. B. (1AD, January 1). Extended amygdala neuropeptide circuitry of emotional arousal: Waking up on the wrong side of the bed nuclei of stria terminalis. Frontiers. Retrieved from

  6. Funahashi, S. (1AD, January 1). Prefrontal contribution to decision-making under Free-choice conditions. Frontiers. Retrieved from

  7. Rhea, E. M., & Banks, W. A. (1AD, January 1). Role of the blood-brain barrier in central nervous system insulin resistance. Frontiers. Retrieved from

  8. Pimentel, E., Sivalingam, K., Doke, M., & Samikkannu, T. (1AD, January 1). Effects of drugs of abuse on the blood-brain barrier: A brief overview. Frontiers. Retrieved from

  9. Authored by Editorial StaffLast Updated: January 7, 2022. (2022, January 7). Effects of drugs & alcohol on the nervous system. American Addiction Centers. Retrieved from


Clinically Reviewed By

Dawn Masick, LMFT

Dawn has experience dealing with various relational, emotional, and psychological struggles. Dawn’s training has prepared her to work with children, teens, young adults, adults, couples, and families. She has undergone training in DBT, TF-CBT, and Family Therapy.  Other competencies include dealing with ADHD, mood/anxiety disorders, parenting challenges, addiction, PTSD, co- dependency, and relationship issues. I have experience in residential, school-based mental health, children’s community mental health, victims of crime (VOC), and private practice settings.

Dawn has been committed to guiding clients through their trauma, coming alongside them in their healing, and supporting them as they navigate life changes. Dawn’s passion is working with clients struggling with trauma in substance abuse and mental health.