The Science of Addiction: How Drugs and Alcohol Hijack the Brain

We all know how drugs and alcohol can affect us. We know the health implications often too.

For example, we’re aware of alcohol’s impact on the liver. We know that cocaine can have a big impact on cognitive functioning. However, what we often don’t know is the science behind alcohol and drug addiction. We don’t know the why, and that can often be instrumental in how we view our relationship with the substances. 

Whether you like to partake in substances, are growing a dependence with them, would like to be further informed of the science behind addiction, it can be valuable information not just to inform your own relationships but be better aware of others’ relationships with substances too. So, here’s a run down of some of the science behind addiction…

The Brain’s Reward System

The main reason we become addicted to substances is due to the way they communicate with the brain’s reward system. 

The brain is wired to seek pleasure and reward, with the likes of eating and social interactions often triggering those and releasing dopamine, the neurotransmitter that produces feelings of pleasure. 

This encourages repeated behaviours, which drugs and alcohol exploit. They flood the brain with dopamine and produce feelings of euphoria. Essentially, this is an artificial high that reinforces substance-taking behaviour, which can be the key player in developing an addiction.

The Role of Neurotransmitters

Substances affect neurotransmitters in different ways depending on what they are. For example: 

Stimulants (e.g. cocaine, methamphetamine)

These increase dopamine levels but also prevent the reabsorption of it, leading to a short but intense high. Over time this leads to the brain producing less dopamine, which makes it harder to experience pleasure naturally. 

Depressants (e.g. alcohol, benzodiazepines)

Depressants enhance the activity of gamma-aminobutyric acid (GABA). This is a neurotransmitter that slows down brain activity and enables us to relax. It places us in a more sedative form. However, chronic use can lead to dependence and withdrawal symptoms from them can include anxiety and seizures.

Opioids (e.g. heroin, prescription painkillers)

A huge problem in society at present, opioid abuse can mimic endorphins and trigger feelings of euphoria that many people seek time and again. As addiction develops, so does tolerance, requiring higher doses to get the same effect. This can increase the risk of overdose significantly.

Cannabis

While cannabis is less likely to be addictive, THC, the active compound in the substance, engages with the brain’s endocannabinoid system, which affects mood, memory and perception, which can be deeply problematic in the likes of relationships and for a person’s mental health. 

Brain Changes Due to Addiction

Repeated substance use leads to lasting changes in the brain, particularly in areas responsible for decision-making, impulse control, and emotional regulation. The key regions affected include:

Prefrontal Cortex

This area is responsible for rational thinking and self-control. Prolonged drug use weakens the prefrontal cortex, making it difficult for individuals to resist cravings and make sound decisions.

Amygdala

This part of the brain processes emotions such as stress and fear. Addiction heightens sensitivity to stress, making withdrawal and cravings more intense.

Nucleus Accumbens

Often referred to as the brain’s pleasure centre, this region is heavily influenced by dopamine surges. Over time, it becomes less responsive to natural rewards, making everyday activities feel unfulfilling compared to drug use.

The Cycle of Dependence and Withdrawal

As addiction progresses, the brain develops a tolerance to substances, requiring larger amounts to achieve the desired effect. Eventually, individuals become physically dependent, meaning they experience withdrawal symptoms when they stop using.

Withdrawal symptoms vary depending on the substance but can include nausea, sweating, anxiety, depression, and severe cravings. These unpleasant effects drive individuals to continue using, trapping them in a cycle of addiction.