What alcohol is and how it acts on the brain

Alcohol is a widely available substance that contains ethanol, a chemical compound found in drinks like beer, wine, and spirits. It functions as a psychoactive drug, meaning it alters brain function and influences mood, perception, and behaviour. Specifically, alcohol acts as a depressant, which slows down activity in the central nervous system, leading to reduced attention, slower reaction times, and impaired cognitive processes.

This depressant effect occurs because alcohol interferes with the communication between neurons, the specialised cells that transmit signals in the brain. To understand this, it is essential to know how alcohol targets key neurotransmitters, the chemical messengers that carry signals across synapses, the gaps between neurons.

Key neurotransmitters affected by alcohol

• GABA (gamma-aminobutyric acid) - An inhibitory neurotransmitter that reduces neural activity by making it harder for signals to pass from one neuron (pre-synaptic) to the next (post-synaptic). Alcohol enhances GABA's effectiveness, further slowing down brain activity. This leads to feelings of relaxation and reduced anxiety, but it can also impair social judgement and encourage disinhibited behaviour.
• Noradrenaline - A neurotransmitter involved in alertness, focus, and the body's fight-or-flight response. Alcohol numbs the nerve endings at noradrenaline synapses, reducing its uptake and making these synapses less effective. As a result, concentration decreases, reflex reactions slow, and the ability to respond quickly in emergencies is compromised, even at low alcohol levels.

By amplifying inhibitory signals and suppressing excitatory ones, alcohol overall depresses brain function. This explains why small amounts might make someone feel more confident and relaxed, while larger amounts can lead to significant impairments in coordination and decision-making.

Short-term and long-term effects of alcohol

Alcohol's effects vary depending on the amount consumed and individual factors, but they generally stem from its depressant action on the brain. It weakens the brain's inhibitory mechanisms, which normally control impulses and social behaviour, leading to a range of physical and psychological changes.

Short-term effects

These occur soon after consumption and can be positively or negatively reinforcing, encouraging further use.

They include:

• Relaxation and euphoria - Low doses reduce anxiety by enhancing GABA activity, creating a sense of warmth from dilated blood vessels and mild happiness, which acts as positive reinforcement (a rewarding feeling that increases the likelihood of repeating the behaviour).
• Reduced inhibitions - Alcohol targets brain areas linked to social control, such as the frontal lobe, which manages planning and self-regulation. This can make behaviour more outgoing or confident initially, but excessive amounts may lead to extreme or inappropriate actions.
• Impaired physical and cognitive functions - Motor coordination decreases due to depressed frontal lobe activity, affecting balance and movement. Judgement, decision-making, speech, and reaction times are also slowed, increasing accident risks.
• Other physiological changes - Dehydration results from alcohol altering hormones that regulate urination, often causing hangovers with symptoms like headaches. High doses can lead to nausea, vomiting, loss of consciousness, or even death from respiratory suppression.

Long-term effects

• Brain changes - Chronic consumption may lead to shrinkage in brain areas, including up to a fifth reduction in brain weight from severe dehydration, exacerbating cognitive impairments.
• Behavioural shifts - Repeated disinhibition can result in risky or antisocial behaviour, with reinforcement from anxiety reduction (negative reinforcement, where removing an unpleasant state like stress encourages the habit).

Development of tolerance to alcohol

Tolerance refers to the body's adaptation to a substance, requiring higher doses to achieve the same effects. For alcohol, this develops through both physiological and psychological mechanisms as the brain and body adjust to its presence.

Physiological tolerance

• Upregulation - As a depressant, alcohol suppresses brain cell activity. The brain compensates by increasing the number or sensitivity of receptors, a process called upregulation, to restore normal function. Over time, more alcohol is needed to overcome this adaptation and produce the initial relaxing effects.
• Enzyme production - The body produces more enzymes that break down alcohol faster. Within weeks, a person may need to consume larger quantities or stronger drinks to feel the same impact.

Psychological tolerance

This arises from repeated exposure, where individuals become accustomed to alcohol's effects and learn to mask intoxication, such as appearing sober despite impairment. It stems from behavioural practice and habituation, making the person feel they can handle more without obvious signs of drunkenness.

Tolerance is a key factor in escalating consumption, as users chase the original effects, which can lead to dependency.

Physical and psychological dependency on alcohol

Dependency, or addiction, occurs when someone relies on alcohol to function, driven by tolerance and reinforcement. It has two main forms: physical, involving bodily adaptations, and psychological, rooted in emotional needs. Both can coexist, with alcohol often used as a coping mechanism for stress or problems.

Physical dependency

This develops from tolerance, where the body needs alcohol to avoid withdrawal.

Characteristics of physical dependency:

• Indiscriminate consumption - Drinkers may consume any available alcohol, including dangerous types like industrial ethanol, which can be fatal.
• Early and constant drinking - Intake starts early in the day to prevent symptoms like irritability or shaking, continuing until blackout to maintain the physical need.
• Withdrawal-driven behaviour - The relief from symptoms reinforces use, creating a cycle where stopping is difficult without medical help.

Psychological dependency

This involves mental reliance, where alcohol is seen as essential for emotional regulation.

Characteristics of psychological dependency:

• Situational reliance - Drinkers feel unable to cope with certain scenarios, like social events or stress, without alcohol, leading to anxiety when it's unavailable.
• Prioritisation and reinforcement - Access to alcohol takes precedence over basics like eating, hygiene, or socialising. Positive reinforcement comes from euphoria, while negative reinforcement arises from anxiety relief. Excessive use may serve as a strategy to handle personal issues, escalating to extreme dependency.

All dependent drinkers experience psychological elements due to reinforcement, but physical dependency adds a constant bodily urge.

Symptoms and risks of alcohol withdrawal

Withdrawal happens when a dependent person stops or reduces alcohol intake, causing the adapted brain and body to overreact. Symptoms typically start 8–12 hours after the last drink and can last up to a week in heavy users.

Common withdrawal symptoms

• Physical effects - Shaking, cramps, nausea, sweating, and irregular heartbeat, stemming from the nervous system's over-stimulation without alcohol's depressant influence.
• Psychological effects - Vivid dreams or anxiety, as the brain struggles to readjust.

Severe withdrawal: Delirium tremens (DTs)

• In extreme cases, DTs can occur, a dangerous condition where the brain, accustomed to enhanced GABA inhibition, becomes hyperactive upon withdrawal.

• Symptoms of DTs - Hallucinations, tremors, delusions, and over-activation of the fight-or-flight response, leading to intense fear or confusion.

• Risks - This can cause seizures, a medical emergency that may result in death if untreated. Sudden cessation is particularly hazardous, requiring professional medical supervision to manage safely.

Withdrawal underscores the risks of dependency, highlighting why gradual reduction or medical support is often necessary for recovery.