The Neurobiology of Addiction
Updated: Jul 25
The brain is the most powerful organ in the human body. It relies on perfectly balanced chemistry to perform all the primary functions in the body. It operates basic functions like breathing, walking, sleeping, and eating, to higher ones like critical thinking, decision-making, and love. However, things like drugs and alcohol can alter the function and structure of your brain, effectively influencing your mental health and well-being. It is important to know how substance use can affect your brain to understand addiction's neurobiology better.
How Can Drugs Interfere with Our Brains?
The brain sends messages to, from, and within the brain using neurons. Neurotransmitters activate in between the neurons to transfer the information from one neuron to the next. Drugs like marijuana and heroin mimic the structure of natural transmitters and can activate neurons. Other drugs, like amphetamine or cocaine, can cause the neurons to release large amounts of natural neurotransmitters or interfere with the "recycling" of brain chemicals. These types of drugs disrupt the natural communication within the brain, changing the way it sends and receives signals.
There are three main areas of the brain involved in drug use and addiction and a three-stage cycle associated with each region:
The Basal Ganglia controls the rewarding/pleasurable effects of substance use. It also plays a vital role in habit formation leading to chronic substance use. This area is associated with the first stage, Binge/Intoxication, when the substance is consumed and the pleasurable, euphoric effects are experienced.
The Extended Amygdala plays a role in the feeling of stress, anxiety, uneasiness, and irritability (the symptoms associated with withdrawal). It is here where the second stage is most associated, Withdrawal/Negative Affects stage. This is the negative emotional state experienced in the absence of the substance.
The Prefrontal Cortex is a part of the brain's executive functions, meaning it is the area of the brain where we organize our thoughts, manage time, problem-solve, make decisions, prioritize tasks, exert self-control, etc. The last stage is the Preoccupation/Anticipation stage, associated with the prefrontal cortex, which is the seeking of the substance again after a period of absence.
And the cycle repeats.
Dopamine is the neurotransmitter most commonly associated with substance use disorders. It is primarily responsible for the pleasure response. The brain uses this neurotransmitter to reinforce beneficial behaviours like eating and socializing. We are more likely to repeat these activities because the brain associates the pleasurable feelings created by the release of dopamine and the activity we are participating in. Its' release also signals to the brain that something is happening that should be remembered and repeated in the future. In this way, dopamine helps lead to the formation of habits.
Drugs produce large releases of dopamine, connecting the intense feelings of pleasure with the consumption of the drug. It also connects the external surrounding and cues to remember, increasing the odds of repeating the pleasurable activity.
How it Works
This process is aided by two major circuits created by neurotransmitters. The reward circuit is over-activated by the euphoric feelings created by the substance high. The reward system associates the pleasurable feelings with the substance leading to cravings and substance seeking. The increasing use of the substance repeatedly activates the habit formation circuit creating a compulsory substance seeking and taking effect. When these two circuits are activated, it can change the way someone responds to stimuli. The dopamine release causes the brain to remember the experience surrounding the substance use, like the people, environment and preceding feelings, which can then become triggers that can create powerful urges to take the substance again.
With repeated use, this circuit adapts to the substance's presence by dulling its sensitivity, therefore making it harder to feel pleasure without drug use. This can create a compulsive escalation in substance use in an attempt to regain the euphoric feelings the reward system once provided. It can also be fueled by the negative feeling associated with withdrawal, which only becomes more sensitive with increased drug use. Increased drug use can be used to get temporary relief from withdrawal symptoms rather than the high.
The executive function of the brain is altered by the reward and habit circuitry, shifting the balance and encouraging drug seeking and reduced impulse control. With addiction, the "go system" is over-activated, relying on the habit-response system and impulsivity. On the other hand, the "stop system" no longer inhibits the go system, promoting more substance seeking.
Recovery is Possible
The good news is that the brain can be rewired due to its neuroplasticity. Many addiction recovery models work to change these patterns. Many medical professionals suggest ninety days as a general estimate for dopamine recovery. However, the damage from drugs can last longer, requiring a year or longer for dopamine levels and brain cells to recover. The brain will naturally want to correct an imbalance when the drug is no longer present.
Looking for help? Nōmina @ Forbidden Plateau is a premier centre for addiction and mental health, specializing in holistic treatment of trauma, addictions, and other complex mental health conditions.