Addiction and the Brain

The pyschology behind addiction.

It may be weakened
Intense drug cravings

The Neuroscience of Addiction

Our brains are made up of billions of nerve cells called neurons, which communicate with each other through molecules known as neurotransmitters. Drugs directly alter this communication process by changing the amounts of a neurotransmitter or mimicking its activity in the brain. This changes how brain areas communicate with one another, leading to short-term changes in mood, perception, thoughts, and behavior.


With repeated drug use, the brain adapts to the presence of drugs by adjusting its chemistry and function. This is related to an important principle of brain function known as neuroplasticity – the ability of the brain to adapt in response to new experiences.

While this brain plasticity helps us learn and adapt, it can also be a double-edged sword in the context of addiction, where prolonged drug use causes the brain to adapt itself to the effects of a drug over time. This leads to tolerance, craving, and withdrawal.

Neurotransmitters and Addiction

Neurotransmitters play a crucial role in the development of addiction. Three key neurotransmitters are dopamine, serotonin, and endorphins.

Dopamine plays a key role as it is involved in motivation and reward. Many drugs cause a surge of dopamine in the brain. This excessive dopamine activity leads to intense feelings of euphoria and the reinforcement of drug-seeking behavior. Over time, chronic drug use can disrupt the brain’s natural dopamine balance, leading to a lack of motivation and a reduced ability to naturally experience pleasure from rewards.


Serotonin, on the other hand, is involved in mood regulation, appetite, and sleep. Drugs such as MDMA increase serotonin levels, leading to feelings of happiness and emotional closeness with others. However, chronic use can deplete natural serotonin levels, contributing to mood disorders, like depression and anxiety.

Endorphins are the body’s natural painkillers and are released after bodily injury as well as during exercise and excitement. Opioids, like heroin and prescription painkillers, mimic endorphins and bind to their receptors, providing pain relief and a sense of well-being. Over time, the brain and body can become reliant on these drugs to produce endorphins, leading to physical and psychological addiction, and severe withdrawals.

Drug Liking vs. Drug Wanting

An important distinction in the neuroscience of addiction is the difference between drug ‘liking’ and drug ‘wanting’. While drug liking refers to the immediate pleasurable experience or euphoria associated with the consumption of drugs, drug wanting refers to the intense desire or craving to consume the drug again.

Drug liking is a direct result of the drug’s ability to activate the brain’s hedonic pathways involved in experiencing pleasure. This is what causes many recreational users to consume drugs, as they hope to recreate the same euphoric feeling they experienced, even if they don’t crave drugs in the same way an addict does.


Drug wanting, on the other hand, refers to an intense desire or craving and is more closely related to the role of dopamine in addiction. It is related to a longer-term process where the brain’s reward system adapts itself to the effects of a drug. This leads to a heightened sensitivity to drug-related cues and an increased motivation to seek out and use drugs.

The distinction between drug liking and drug wanting is important because while drug liking can diminish over time, drug wanting can persist even long after the drug’s pleasurable effects have worn off. This helps us understand why compulsive drug-seeking behavior can occur despite the severe negative consequences.

The Prefrontal Cortex and Impulse Control

The prefrontal cortex (PFC), located at the front of the brain, plays a crucial role in decision-making, impulse control, and the regulation of emotions. In addiction, the PFC becomes compromised, leading to impaired decision-making and an increased likelihood of engaging in risky behaviors.

One example of this impairment is ‘delay discounting,’ where individuals with addiction often choose smaller, immediate rewards, such as drug use, over larger, delayed rewards, such as long-term health and well-being. This preference for immediate gratification can contribute to the cycle of addiction, as individuals prioritize the short-term benefits of drugs over other aspects of their lives.


The PFC also plays a role in inhibiting impulsive behaviors, such as drug-seeking. In individuals with addiction, this inhibitory function may be weakened, leading to an increased likelihood of relapse as they struggle to inhibit their destructive pattern of behaviors.

Stress, Addiction, and the HPA Axis

The connection between stress and addiction is well-established, with stress often serving as a trigger for substance use and relapse. The hypothalamic-pituitary-adrenal (HPA) axis is a key player in the body’s stress response, releasing stress hormones like cortisol in response to perceived threats. Chronic stress can dysregulate the HPA axis, leading to increased vulnerability to addiction.


Drugs can also activate the HPA axis, further reinforcing the connection between stress and addiction. On the other hand, alcohol and opioids can suppress the HPA axis, leading to a temporary reduction in stress. However, this suppression can also contribute to the development of addiction, as the brain becomes reliant on the drug to regulate stressful feelings.

The amygdala is another important brain region that is involved in the stress response and addiction. It is responsible for processing emotions, including fear and anxiety, and can become hyperactive in individuals with addiction, leading to increased stress and drug-seeking behavior.

Brain Plasticity and Habit Formation

Habit formation is a key aspect of addiction, as repeated drug use can lead to the development of automatic, compulsive behaviors. The brain’s reward system plays a crucial role in habit formation, reinforcing drug-seeking behavior through the release of dopamine. Over time, these habits become deeply ingrained, making it difficult to overcome one’s addiction and break out of a vicious cycle of dysfunctional behaviors.

However, the same brain processes that contribute to addiction can also be harnessed for recovery. By engaging in new, healthy behaviors and experiences, individuals can create new neural pathways that support sobriety and well-being. While this may be very difficult at first, as time goes by, the brain will start to adapt itself to sobriety and start to experience natural pleasures once again. This process of “rewiring” the brain can help people overcome their addiction and develop healthier habits.

Although the brain can learn and adapt itself to a sober lifestyle, the old patterns of addiction can be hard – if not impossible – to fully unlearn. Even many years after abstaining from drugs, consuming small amounts can activate the same old neural pathways, which can quickly lead to the same old pattern of addictive behaviors. This is why life-long abstinence is such an important principle in drug recovery programs.

The Role of Context on the Brain in Addiction

Context can influence the brain’s response to drugs and contribute to the development of drug-seeking behavior. One example of this is Pavlovian conditioning, a form of learning in which a neutral stimulus becomes associated with a rewarding or negative event. In the case of addiction, drug-related cues, such as the sight or the smell of a certain substance, can become associated with the pleasurable effects of the drug.

These contextual cues can act as a risk factor for relapse as they can trigger intense drug cravings even years after abstaining from drugs. This can make it difficult for former addicts to revisit contexts, such as people or places, which are linked to their past drug use.


The context in which a drug is used can also be a risk factor for overdose due to ‘situational-specific tolerance’ – where someone person builds up a tolerance to the effects of a substance in specific, familiar circumstances. When drugs are being used in a new context, their effects might therefore be more intense in comparison to the familiar context. This increases the risk of an overdose for drugs like heroin and cocaine.

The Role of Social Connections

Social connections can influence someone’s susceptibility to drug use and addictive behavior. The Rat Park study, conducted by Bruce Alexander and colleagues in the 1970s, is a great demonstration of this.

In this study, two groups of rats were given the choice between drinking normal water and morphine-laced water. Group A was housed in individual isolated cages, and almost instantly preferred consuming the morphine water over the normal drinking water. Group B was housed in Rat Park – a large, stimulating, and social environment. Unlike the rats in isolated cages, the rats in Rat Park would try the morphine water occasionally, but they generally preferred the normal drinking water.


These findings highlight the importance of social connections in addiction, as rats in the enriched environment were less likely to develop addiction-like behaviors. Similarly, humans with strong social connections and support networks are less likely to develop addiction and more likely to achieve long-term recovery.

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