Addiction and the Brain: How Substance Abuse Affects Mental Function 

Addiction and mental health are closely linked because substance use disorder is about more than using and feeling the effects of drugs or alcohol. It comes from complex interactions between chemical neurotransmitters, internal brain structures, environment, and genetic tendencies. 

Medication-based treatments can work well for this reason. Addiction is a physical ailment, not a sign of weak willpower or moral failure. Addiction cravings are entirely involuntary, caused by unhealthy “neuroadaptations.” 

Drug use changes the brain, just as asthma changes the lungs and hypertension alters the heart. The nervous system relies on drugs for neurotransmitters and dopamine rather than manufacturing them alone. Critical structures in the base of the brain develop unnatural proportions that create equally unnatural behaviors. 

Dopamine, Addiction, and the Brain’s Rewards System 

Drug addiction overwhelms the natural pleasure centers of the brain, which rely on dopamine. The reward center is a good and natural part of the brain that encourages survival-promoting behaviors in primitive humans. Doing things that promote survival and reproduction feel “good:” 

• Eating sugary foods or protein-rich meats
• Having sex
• Moderate exercise 
• Conserving energy and sleeping

Drugs trigger a dopamine rush, which is a reward for doing nothing at all. The body, a survival- and efficiency-driven machine, pursues the most benefit for the least effort. Drugs produce more good feelings for less effort, and the body and brain can’t tell the difference or recognize the danger.

The brain “learns” through repetition. Over time, it “teaches” itself to “recognize” indicators of impending substance abuse, called triggers. Certain people, places, or other sensory inputs trigger a reflexive craving for dopamine from drugs. Patients must fight against their brains’ new instincts to avoid relapsing. These triggers are deep-rooted behaviors and remain active months or years after sobriety. 

Mental behavior changes through two primary channels: changes in neurotransmitter levels and permanent alterations to brain structure. 

Changes to Neurotransmitters 

Neurotransmitters are chemical messengers that flow between nerve cells. They control everything the body does, from breathing and heart rates to the highs and crashes in drug use. 

What are Neurotransmitters? 

Neurotransmitters are chemicals that flow between neurons across ‘synaptic junctions” between cells. They bind to receptors at the other end of another neuron. The second neuron then sends a similar signal or performs an action. Different transmitters make the neuron send or block messages to other neurons, causing the body and brain to act. 

Drugs either mimic neurotransmitters or force the neurons to release too many at once, depending on the drug’s “mechanism of action.” Both actions cause a massive chemical surplus, which triggers nerves too often. 

Prolonged drug use makes neurons more accustomed to these higher chemical levels. It needs fewer receptors because so many neurotransmitters flow across those gaps that the remaining receptors will send all the necessary signals. Those “excess” receptors become nonfunctional. When this happens, the patient needs drugs to make their neurotransmitters function as they should. They then need even more neurotransmitters to achieve a high—requiring a higher dosage of their drug of choice. This change in level requirements is called a “tolerance.” 

Artificial Neurotransmitters 

The natural chemical structure of certain drugs’ active ingredients fit into neurotransmitter receptors in a neuron. The neuron receives the same “instructions” from these chemicals and natural neurotransmitters and sends the same signal. Many neurotransmitters flood the gaps between neurons and send their signals repeatedly.

Neurotransmitter Overload 

Other drugs force the body to overproduce natural neurotransmitters, causing the same effects. Cells respond more than they should, firing off signals that natural chemical levels can’t match. These signals trigger pleasure, excitement, and joy, or other negative emotions like paranoia and anger—common side effects of drugs.

Chemical Tolerance 

During periods of sustained use, neurotransmitter-making brain cells scale back their production. Evolution designed the human body to conserve resources whenever possible. So far as the body is concerned, Drugs give neurotransmitters (or close equivalents that work just as well, so far as the body’s concerned) from an external source. The body doesn’t “see” a reason to make as many neurotransmitters when so many come from outside. Lower production means lower natural transmitter levels, creating a deficit when the drug wears off. 

At this stage of high tolerance, cravings shift from high-seeking to relief-seeking. Most people reach a healthy baseline without drugs. People with addictions need their drugs to reach that level. The brain, therefore, creates powerful cravings to help them achieve that new normal. 

Brain Structure Changes from Drug Use 

The brain is an intricate and not fully understood organ. Dozens of complex parts interact with one another, causing enormous chain reactions. Though addiction affects the entire brain, it alters three structures most: the basal ganglia, the extended amygdala, and the prefrontal cortex. 

Basal Ganglia 

This set of interconnected structures deep in the brain controls habit-forming behavior. They create motivation by “rewarding” the rest of the brain for “good” survival-promoting actions. The pleasure chemicals released when eating, having sex, or sleeping encourage the body to repeat them. 

They also “punish” the brain when it doesn’t receive them through cravings for certain nutrients or exhaustion. In time, it comes to associate drugs with pleasure over all other options. It pushes addiction patients to get more when they don’t have any, even at the cost of their health and loved ones. 

Extended Amygdala 

The extended amygdala controls stress. Damage to the brain due to extended drug use makes it release stress hormones as neurotransmitter production drops during long periods between highs. Stress hormones indicate something’s gone wrong, and the brain tries to reduce or eliminate them at any cost. 

Drugs are the most immediate and intense release from cravings. They replace stress hormones with pleasure chemicals and address the brain’s only underlying concern—neurotransmitter shortage. “Knowing” this, the amygdala pushes the brain to create involuntary drug-seeking compulsions to calm stress as fast as possible. 

Prefrontal Cortex

The prefrontal cortex controls executive function—rational decision-making, motivation, and delayed gratification. The structure physically shrinks in current and former addiction patients, and the ability to make healthy decisions diminishes with it. Cravings, already compulsions with incredible power, easily overpower the weakened cortex. 

Break the Cycle With Dual Diagnosis Treatment 

Los Angeles patients should consider a stay at SoberMind’s sober living facilities. Their resources help face these physical and chemical changes. Science doesn’t have all the answers, but it’s always possible to self-reflect and take medications. Medical practices know ways to treat addiction even if the underlying mechanisms aren’t yet clear. 

Contact SoberMind Recovery to learn more about its programs and how they help. Its dual-diagnosis treatments address both addiction and illnesses like depression and anxiety that accompany it.