Why is it that some people get aggressive and violent when they are drunk?
Why is it that some people get aggressive and violent when they are drunk? Anastassia Perets

Why do some people get violent when they are drunk?

WITH another man convicted of a coward punch at Gympie's Monkland St taxi rank this week, it is hard to fathom why some people turn aggressive and violent when they drink.

Subtle differences in brain function, personality and social development play major roles.

How alcohol can make us aggressive

"Alcohol reduces our ability to think straight," says Professor McMurran, a psychologist at the University of Nottingham on the website drinkaware.co.uk.

"It narrows our focus of attention and gives us tunnel vision," says Prof McMurran.
"If someone provokes us while we're drunk, we don't take other factors into account, such as the consequences of rising to the bait. This can lead to violent reactions from people who would usually shrug things off."


Alcohol causes chemical changes in the brain which can initially make you feel relaxed, which can be one of the reasons we enjoy drinking, drinkaware.co.uk says.

But, according to Professor McMurran, anxiety actually protects us by telling us to avoid or escape certain situations.

"When we're drunk, this warning system doesn't work and this can put us in dangerous or confrontational situations."


The way we process information is affected when we've been drinking too. We're more likely to misinterpret other people's behaviour and misread social cues. This could be the reason why so many drunken fights start over little more than a 'dirty look'.


Avoiding aggressive encounters

The majority of people who drink are never violent and even those who do become aggressive won't do so all the time. Still, losing your cool over something as simple as a spilled drink is never a good move.
 Binge drinking increases the likelihood of both becoming aggressive and of being on the receiving end of someone else's temper1.

 If you're wanting to cut back on alcohol or simply want to keep track of how much you're drinking, our free Drinkaware: Track and Calculate Units app or MyDrinkaware tool can help.

Alcohol-related violence makes far too many headlines with increasing frequency in the Gympie region and across Australia, but not everyone who drinks alcohol, even to excess, becomes aggressive.

In fact it's only a small minority, says psychologist and Stanford University substance abuse researcher, Dr Adrienne Heinz on drinkaware.co.uk.

"Very few people when they drink actually become aggressive," says Heinz.

But their behaviour can have far-reaching consequences. Families and friends can be the targets of alcohol-fuelled outbursts, as can other unsuspecting members of the public.

"Alcohol remains clearly the most important drug to be addressed as far as harm is concerned," says Dr David Caldicott, emergency medicine consultant at the Calvary Hospital in Canberra.

Who's at risk?

For Caldicott, who regularly sees the results of alcohol-related violence, personality is a key element that separates aggressive drunks from everyone else.

"I think the reality is that the sort of people who are going out and hitting other people [when drunk] are the sort of people who would go out and hit other people [when sober]," he says.

Studies of alcohol and aggressive behaviour square well with Caldicott's observations. People who are more irritable, have poorer anger control, and who display lower levels of empathy towards others when sober, are more likely to be aggressive when they have alcohol in their system.

Gender also has an influence: men are more likely than women to be aggressive when drunk.

Out of control

There is increasing evidence that subtle variations in brain function mean some people behave worse than others when they have a few drinks.

One way in which alcohol's effects on brain functioning have been measured is to look at how people use what's known as the brain's executive system. Decision-making, problem solving and reasoning are all jobs the executive system takes control of. As Heinz explains, it is like the command centre of the brain, that "tells you when to put on the brakes, think about the consequences, steer yourself towards a better long-term outcome."

But when we drink alcohol, executive control flags, making it harder to reflect on our behaviour and self-regulate. Instead of taking a few deep breaths when we feel slighted or insulted, we give in to our impulses, which for some are violent.

Importantly, some people naturally have poorer executive control than others, and these people, particularly if they are male, are more likely to be aggressive after drinking alcohol.

A lack of executive control could also help to explain why adolescents and young adults are so frequently the perpetrators of violent behaviour when drunk. It has been shown that our brains continue to develop well into our 20s and that one of the last parts of the brain to develop is the prefrontal lobe, the region responsible for reigning in impulses through executive control.

People who have a dependence on alcohol have a "double whammy" when it comes to executive control, according to Heinz. Each time they consume alcohol, their executive functioning is impaired due to the alcohol in their system. But their consistent use of alcohol also leads to poorer executive function even when they aren't drinking, an effect that can last for up to a year after they stop drinking.

According to drinkaware.co.uk, studies on rats have shown that, as in humans, only a small proportion of individuals become aggressive when inebriated. The studies also show that rats with lower levels of the brain signalling chemical serotonin, and higher levels of another called dopamine, are more likely to be aggressive when given alcohol. (Such brain signalling chemicals are known as neurotransmitters.)

Similar changes in both of these neurotransmitters have been found in chronic alcohol drinkers, and it is believed likely they play a role in violence in non-alcoholic binge drinkers too. People with lower serotonin levels are also known to be more likely to consume alcohol to the point of excess. Since early life trauma and adversity can alter serotonin signalling, these factors have potential to raise the odds of a person having a short temper when drunk.

Alert and alarmed

When someone accidentally bumps into you in a crowded bar or at a sporting event, most of us are able to quickly shrug it off as a benign interruption to our day. But add alcohol to the equation and an innocuous bump can suddenly be interpreted as a serious threat, or even a deliberate act of aggression.

"[Alcohol] can affect information processing and your ability to determine how much threat is actually present in the environment," says Heinz.

Caldicott agrees that alcohol "alters our perception of the world," and explains that any increased sensitivity to perceived threats isn't just about what's going on in the brain. Alcohol's effects on the heart can also play a role. "You can get palpitations, or what we call tachyarrhythmias, as a consequence of alcohol," he says, and a racing heart can often be misinterpreted as a threat.

Expectations matter

For Heinz, one of the most interesting areas of individual difference when it comes to alcohol-related aggression is in what we expect to happen when we get drunk. Expectations about what behaviour is normal and socially acceptable when alcohol is consumed can be set in place long before we take our first sip of beer.

"You actually see these [expectations] in pre-schoolers and young children who've never had any experience with alcohol before," says Heinz. How our parents act when they drink can lay down our first impression of alcohol-related behaviour. As we get older and see how our friends and others in the community behave, associations between alcohol and aggression can become stronger if that's what we see around us.

"In a society where there's a lot of pub-related violence, or violence that's seen when you're drinking at sporting events, it becomes [more] socially condoned," she says.

The power of expectation can also play a part in influencing how people behave when they consume different alcoholic drinks, quite apart from the physical impact of differing alcohol concentrations, Heinz believes. "People have different expectations for what happens when I drink wine versus when I drink liquor versus when I drink beer," she says.

Whether certain drinks, such as those with high levels of sugar or caffeine, help to enhance aggression is unclear, although Heinz notes that alcoholic drinks that contain caffeine can lead people to take more risks than they otherwise would.

Curbing violent behaviour

With people who are more likely to be aggressive when they drink, one of the greatest challenges for psychologists like Heinz is teaching temper control, says drinkaware.co.uk. She says that anger management programs are a good start for those who end up seeking help when alcohol gets them into trouble with the law or their families.

"You create safety plans, you learn the internal sensations of anger, how to identify them and then what to do to turn down the volume when things are a bit hot."

Heinz is also looking into whether therapy to improve people's executive control might help.

But when it comes to reducing the number of people turning up at hospital emergency departments due to alcohol-related violence, Caldicott believes limiting overall community alcohol consumption would be of clear benefit.

"If you have a toxin that's causing harm in the community, it's up to public health to ensure that there are limits on the availability of that toxin," he says. "It's not rocket science."

Gympie Times


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