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Lesson 2: The Neurochemistry of Addiction

This week, we are going to focus on understanding the neurochemistry of addiction. It’s not enough that we recognize how our behaviors and thought life create problems in relationship. To gain lasting sobriety from any destructive behavior, we have to learn what’s happening in our brain so we can initiate change from the inside out.

As we dig into our past throughout the course of this study, we will discuss many factors that contribute to addictive and problematic behavior. Typically, it is not one single life event or circumstance where coping behaviors were developed to soothe the painful feeling in the moment. It is important to recognize that the road to addiction is multifaceted and often explained through a biopsychosocial perspective—meaning that our biology (genetic and chemical makeup), psychology (mood, personality, behavior), and the social environment (culture, family, socioeconomic status) of our life each plays a role in our behaviors.

The brain structures and functions discussed in this lesson will provide a foundation for all neurochemistry discussions in the following lessons.

Jesus replied, “‘You must love the LORD your God with all your heart, all your soul, and all your mind.’

We are commanded to love God with our heart, soul, and mind; but how can we do this if we don’t understand how our mind—our brain—works and contributes to our behaviors?

While it is not necessary to know all the intricacies of the brain, it is essential to know both the structures and functions of some basic processes. For this reason, this lesson is primarily about learning what we need to know—what is necessary for creating a road map to recovery—followed by practical application.


The human brain is one of the most mysterious of God’s creations. It contains approximately 100 billion nerve cells or what we refer to as neurons. 14 A single neuron communicates or sends information by passing a chemical—a neurotransmitter—to another neuron. The connections between neurons—the synapse or synaptic gap—can span from 10 trillion to 100 trillion points of contact within the human nervous system.


The primary function of a neuron is to process information.16 Neurons vary in both form and size depending on their specific function; some less than fractions of an inch and others up to 3 feet in length. They are also specific to which type of neurotransmitter they respond: dopamine, serotonin, or norepinephrine, for example. In very simple terms, an electrical impulse travels down the axon, producing a chemical reaction— releasing neurotransmitters into the synaptic gap. A receptor on the receiving cell will bind to a specific neurotransmitter, in many ways reflecting a lock-and-key scenario, absorbing the neurotransmitter, yielding a specific action.

This is called synaptic transmission. The excess neurotransmitters not used by the receiving cell are taken back into the sending cell—recycled—through a reuptake process for repackaging and reuse.17 Although this process is extremely complex, down to the most minuscule detail, it is important to understand how these mechanisms work in connection to addictive behavior.

The limbic system is located in the center of the brain—often referred to as the emotional center of the brain. It is not one isolated part of the brain, but rather a collection of structures associated with processing emotion, mood, and memory.18 The limbic system is made up of several distinct areas, interconnected by their function. Three specific areas of the brain play a significant role in addictive behavior.

The prefrontal cortex, which interacts with the limbic system, does many amazing things for us: regulates positive and negative emotion, helps with problem-solving, and self-awareness, to name a few.19 Most importantly, when it comes to addictive behavior, the prefrontal cortex contributes to decision-making, planning, and impulse control.

The hippocampus gathers information from many sources—from our environment and life events—and links them together to form memories.20 It is responsible for consolidating (moving) our short-term memory into long-term memory while we sleep (another reason why sleep is so important).

The amygdala regulates our emotional response and assigns meaning based on our environment.21 Both positive and negative emotions are produced in the amygdala as a result of a rapid assessment of the situation. For example, when someone we love walks into the room, our face will display an emotional response of happiness or pleasure. Or, if someone unexpected appears in a dark setting, we may respond with fear because the amygdala has determined that there is a threat or the situation may be dangerous.

When we have an experience, especially an event that is perceived as threatening or dangerous, the hippocampus and the amygdala work together to process the event—the specific details of what happened and the way it made us feel are stored together in our limbic system.

The disconnect: research suggests that the limbic system—the emotional center of the brain—is fully functional by age six.22 However, the prefrontal cortex—decision-making, planning, and impulse control—is not fully developed until the mid-twenties.

The reality of this physiological disconnect: most of us will spend almost 20 years interpreting our world—what is happening to us and around us—through a highly emotional filter; through a limbic filter. Not because we are overreacting or overly emotional, but because our brain is not yet capable of rational thought.

I couldn’t understand my reaction. The look on my husband’s face was that of shock, confusion, and disappointment. We were out on a date, having a great time, when he leaned in to kiss me. Without even thinking about it, I turned my head and pulled away. In the moment, I felt the need to protect myself; but why?

As a girl, I remember boys trying to kiss me when I didn’t want them to. In high school, with many boyfriends, they kissed me aggressively—like they were taking something from me that I was not willing to give. At times, especially in sexual situations, they forced themselves on me, trapping me into submission. I felt afraid and unsafe. I had no control over what was happening to me.

This doesn’t make sense. If I’m in a happy, committed marriage, why would I respond to my husband this way? I really love kissing him, so why is this happening?


God designed our limbic system for survival, to help us develop awareness and learn from our environment—whether we are safe or in danger. Collectively, the areas of the limbic system work together to influence and create emotion, mood, and memory. In response to an emotional trigger—a limbic reaction, if you will—the limbic system will set in motion a sequence of neurological actions.

If a situation is alarming or frightening, it will trigger our fight-flight-or-freeze response.23 If we encounter a person as a friend, our memory will override the need or feeling to retreat, and produce the appropriate warm-hearted response.

Our limbic system is so important. When the Bible refers to our heart—when we ask Jesus into our heart—it is referring to this area of the brain: the limbic system. When it comes to our sexually compulsive and addictive behaviors, lifelong healing comes from a renewing of our limbic system.

Everything we do— all of our thoughts, feelings, and behaviors—originate in our brain. The motivation behind why we do what we do happens through a specific process. Here’s how this works.

The ventral tegmental area (VTA) is highly responsive to the production of dopamine.25 This is the origin of the dopamine system. It looks for excitement or novelty (stimulation) in our environment. Once it finds excitement, the release of dopamine increases and is projected to various regions of the brain: the nucleus accumbens, amygdala, and hippocampus of the limbic system, and the prefrontal cortex.

When dopamine is stimulated in the brain, it creates feelings of euphoria and pleasure. Who doesn’t want that! When we participate in behaviors that stimulate the production of dopamine in our brain, we naturally want to repeat those behaviors. The reward system doesn’t just create feelings of pleasure. It includes areas of the brain involved with motivation and memory. Logically, we determine that if we continue the same behaviors, we will get the same response. If it were only that simple.

Dopamine is a powerful motivator. In laboratory studies, rats will perform a specific action to receive an electrical stimulation to their brain—rewarding them with the production of dopamine—ignoring all other rewards such as food and water.26 When it comes to stimulating the production of dopamine, rats will press a lever as rapidly as 2,000 times per hour, each time receiving an electrical stimulation. In fact, they will continue to press the lever at this same rate for 24 hours or more. This is just one example of the power of dopamine.


Have you ever thought of addictive behavior as learned behavior? Think about this: learning produces changes in the way we think, feel, and act.28 When our behavior is reinforced with a positive result—making us feel in control, happy, or safe—we naturally want to repeat the behaviors that created this specific response. The more we repeat the behavior, the more it changes our brain, strengthening neural connections.

Previously, we learned what is happening during synaptic transmission: the communication process among neurons in a healthy, non-addicted brain. Here’s what is happening in an addicted brain.

The best way to illustrate this process is to begin with a brain addicted to cocaine. When an individual uses cocaine, it activates the VTA, stimulating the production of dopamine.29 However, with cocaine on board, the cocaine binds to the dopamine transport system and blocks the reuptake process. As a result, dopamine floods the synaptic gap and over stimulates the receiving neuron.

What is most fascinating about this process is that the brain registers all pleasure the same way, regardless of its origin. 30 Whether we derive pleasure from shopping, a substance, a sexual encounter, or an accomplishment, the brain responds the same way. In fact, the brain doesn’t discriminate based on the source—it will continue to produce dopamine in response to the stimulation of the VTA.

So what is happening in the brain if cocaine is not the issue but a behavior is the issue? What is blocking the reuptake of dopamine? This is an excellent question.

Based on research from the University of Florida, scientists liken the dopamine transport system to a very powerful and efficient “vacuum cleaner.”31 In a healthy brain, when dopamine is released in response to a pleasurable action, dopamine is eventually swept back into the sending cell via the dopamine transport system, returning the brain to a less-stimulated state. Our brain is all about balance. When the dopamine transport system is out of balance—unable to keep up with excessive amounts of dopamine in the system—problems occur.

A non-substance addiction is considered a behavioral or process addiction: the compulsion to continually engage in a behavior despite the negative consequences.32 When it comes to addictive behaviors, we all can find ourselves becoming addicted to love, sex, food, shopping, relationships, gaming, and even social media. Our brain can become addicted to these behaviors the same way it becomes addicted to a substance.


Typically, when our reward system is naturally stimulated through the pleasures of our everyday lives, our brain functions accordingly. However, when we artificially increase the stimulation of dopamine through substance use or behaviors, flooding the brain with dopamine, the brain responds by producing less dopamine.33 The brain recognizes when something is not right in its chemical makeup and makes adjustments to bring everything back into balance. Over time, the substance or behavior yields less pleasure, requiring an increased dosage of the substance or an escalation in the behavior to achieve the same dopamine high.

When it comes to developing tolerance, here’s what we need to remember: an increase in stimuli—the substance or behavior used to make us feel better—decreases the effect it has in the brain.

This is also one of the main reasons why it is so difficult to stop using a substance or engaging in an unhealthy behavior. The downside of a dopamine high is often followed by anxiety and depression34—anxiety because we’re now faced with living life without the protection of our addiction, and depression because our brain has decreased its dopamine production.


All of this brain information would be incomplete without recognizing the practical way it impacts our relationships, especially when it comes to our emotional health.

Understanding the factors that influence emotion is challenging; however, emotion plays a significant role in our everyday lives, shaping and enhancing the human experience. It is important to recognize the difference between mood and emotion. Mood is often defined as a more persistent period of emotionality.35 Emotions are typically short-lived, lasting anywhere from a few minutes to several hours, and often occur in response to an external stimuli.

We’ve all been there. It can be caused by another driver who almost hit our car, the past-due notice we get for the bill we’ve already paid, or the red sock that found its way into our laundry load of whites, and we now have the wardrobe of a pretty pink princess. We feel alarmed, exasperated, and frustrated (and a little sad), but only in the moment. These feelings soon fade and are replaced when our emotions are again evoked.

Experiencing emotion involves both physical and mental processes, which are dependent on what’s happening (external stimuli) and an individual’s interpretation of the event.

While it has been argued that we have six basic or universal emotions—joy, sadness, anger, disgust, fear, and surprise—this remains a topic of controversy.37 Not only are the terminology and definitions used ambiguous at best, emotion is subjective. While we may be able to infer, generally speaking, that in a general situation most people would emotionally respond in generally the same way, this is dangerous. Cultural influences, issues of mental health, and individual life experience profoundly affect emotion. More importantly, all other emotions—love, delight, empathy, passion, gratefulness, and many more—are learned behavior.

When it comes to the development and regulation of interpersonal relationships, emotional expressions are crucial.39 Much of human interaction relies on, and is often dictated by, our ability to learn and recognize emotional or facial expressions. Here are a few examples to illustrate this point:

  • An infant will learn facial expressions from their primary caregivers—both positive and negative—during their early attachment years.
  • When a teenager comes home from school, aggressively throws his backpack on the floor and yells at his brother, he is greeted by his parent with a defensive but curious facial expression, reacting to his hostility.
  • While appearing in court after receiving a speeding ticket, the judge’s somber expression and serious tone often set the mood for everyone in the room.

There are many instances we could discuss where we had the opportunity to practice our facial expression awareness. Throughout the course of this study, we will continue to build on what we learned about brain structure and function and the way it contributes to our behavior.

Keep in mind that understanding emotion is more than our ability to recognize emotional or facial expressions. Emotion can also be the result of an internal stimuli—a feeling or a thought that creates an emotional response.

Looking Ahead

Complete the Group Check-In, Self-Care lesson, Thoughts/Feelings Awareness Log,
and Change & Growth Analysis in your Unraveled: Weekly Tools before
the next group meeting.