Living with neighbourhood violence may literally shape teenagers’ brains

Protesters against gang violence in South Central Los Angeles, 2011. Image: Getty.

Flinching as a gunshot whizzes past your window. Covering your ears when a police car races down your street, sirens blaring. Walking past a drug deal on your block or a beating at your school.

For kids living in picket-fence suburbia, these experiences might be rare. But for their peers in urban poverty, they are all too commonplace. More than half of children and adolescents living in American cities have experienced some form of community violence – acts of disturbance or crime, such as drug use, beatings, shootings, stabbings and break-ins, within their neighbourhoods or schools.

Researchers know from decades of work that exposure to community violence can lead to emotional, social and cognitive problems. Kids might have difficulty regulating emotions, paying attention or concentrating at school. Over time, kids living with the stress of community violence may become less engaged in school, withdraw from friends or show symptoms of post-traumatic stress, like irritability and intrusive thoughts. In short, living in an unsafe community can have a corrosive effect on child development.

Few studies, though, have specifically looked at the toll community violence may take on the growing brain. Recently, I studied this question in collaboration with a team of researchers here at the University of Southern California. Our goal: to see whether individuals exposed to more community violence in their early teen years would show differences in the structure and function of their brains in late adolescence.

Witnessing crime has lots of downstream effects. Image: ATOMIC Hot Links/creative commons.

Connecting community violence to the brain

My colleague Gayla Margolin, an expert on youth exposure to violence, has been following a sample of Los Angeles-area youth for over a decade. When these teens were about 13 years old, she asked them to fill out a checklist of community violence experiences: hearing gun shots, witnessing a beating, seeing someone do drugs, watching someone get arrested or chased by the police, seeing someone get chased by a gang, or seeing someone get threatened with a beating or stabbing. For our current study, we added these items together to get an overall sense of how much violence each teen had witnessed in his or her neighbourhood.

About four years after they took the community violence survey, when the youth were around 17 years old, we asked 22 of them to lie down in a magnetic resonance imaging (MRI) machine while we scanned their brains. When we examined the images we’d collected, we zeroed in on two small but critically important structures near the base of the brain: the hippocampus and the amygdala.

The hippocampus, a curved structure shaped like the seahorse it is named after, plays a role in learning and memory. Stress hormones seem to shrink this structure, and adverse childhood experiences like abuse and neglect have been linked with smaller hippocampal volumes later in life. One recent review of research on child maltreatment found that early abuse and neglect predicted smaller hippocampal size in 30 out of 37 studies that looked at the connection.


In our current study, we also measured the size of the amygdala, an almond-shaped structure located close to the hippocampus that is known for its involvement in emotion and threat-related processing. Childhood adversity has also been tied to the size of the amygdala, although this research has been mixed: Some studies have found that people exposed to early stress show smaller amygdala volumes, some show larger amygdalae and some show no relationship at all.

In addition to looking at the size of the hippocampus and amygdala, we also looked at patterns of interconnection between these structures and other regions of the brain. Which parts of the brain “talked” more to each other, as reflected by more tightly correlated levels of activation?

A neural signature of community violence?

In our data, we found that witnessing violence in early adolescence predicted smaller volumes of both the hippocampus and amygdala in this group of teens.

We didn’t measure the absolute size of these structures – instead we tested the relationship between community violence and brain volume. In other words, if our participants told us at around age 13 that their neighbourhood were higher in crime and violence, the size of these critical brain structures looked smaller about four years later, compared to teens who reported less community violence. Interestingly, this link held up even after we controlled for the youth’s socioeconomic status (family income and education) and their present-day exposure to community violence.

These brain regions showed stronger connectivity with the hippocampus among youth exposed to greater community violence. Image: Darby Saxbe/creative commons.

We also found that, among youth exposed to more community violence, the right hippocampus showed stronger connections with other brain regions linked to emotion processing and stress, perhaps suggesting that these youth were more vigilant to potential threat. If you’re used to encountering dangerous situations, maybe you and your brain learn to stay alert to avoid the next potential threat that lurks around the corner.

Our study dovetails with other research on early stress and the brain but is the first to specifically look at the link between community violence and the size and connectivity of the hippocampus and amygdala. Our sample was quite small and limited by the fact that we scanned the youth only once, in late adolescence. Therefore, although our measure of community violence was collected about four years before the scan, we have no way of knowing for sure whether community violence actually led to changes in the hippocampus and amygdala. It’s possible these brain differences preceded the youths’ exposure to community violence. For these reasons, this study should be considered preliminary and needs to be corroborated by much more research.

Despite its limitations, this work takes a first step in showing that community violence is linked with detectable differences in the teen brain in ways that are consistent with other forms of early adversity like abuse and neglect. These effects might be due to stress hormones that flood the developing brain and affect the growth of neural structures like the hippocampus and amygdala.


Youth with smaller hippocampal volumes may show learning and cognitive difficulties, whereas smaller amygdala volumes have been linked with depression risk and behavior problems. In other words, if, as we suspect, community violence has a toxic effect on the brain, downstream effects may emerge both at school and at home. And those effects converge with the deficits in attention, cognition and emotion regulation that other researchers have already noted in youth exposed to community violence. They may even endure into adulthood and contribute to a cascade of risk for further problems in employment and education.

Although community violence may be widespread, that doesn’t mean it’s acceptable. Developing kids and teens deserve to feel safe at home, in their schools and in their neighbourhoods. As our results and those of many other studies show, growing up in a violent or chaotic environment seems to leave traces on the brain, and may put youth at risk for other problems down the line. Although we don’t usually think of street lights, after-school programs and revitalised park spaces as brain-building improvements, public investment in urban neighbourhood safety and quality may have wide-ranging benefits for teens at risk.

Darby Saxbe, Assistant Professor of Psychology, University of Southern California – Dornsife College of Letters, Arts and Sciences.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Covid-19 is highlighting cities' unequal access to green space

In the UK, Londoners are most likely to rely on their local park for green space, and have the best access to parks. (Leon Neal/Getty Images)

As coronavirus lockdowns ease, people are flooding back to parks – but not everyone has easy access to green space in their city.

Statistics from Google show that park attendance in countries across the globe has shot up as people have been allowed to move around their cities again.

This is especially true in urban areas, where densely populated neighbourhoods limit the size of private green space – meaning residents have to go to the park to get in touch with nature. Readers from England can use our interactive tool below to find out how much green space people have access to in their area, and how it compares to the rest of the country.

 

Prime Minister Boris Johnson’s announcement Monday that people are allowed to mingle in parks and gardens with groups of up to six people was partially following what people were doing already.

Data from mobile phones show people have been returning to parks across the UK, and also across Europe, as weather improves and lockdown eases.

People have been returning to parks across the world

Stay-at-home requirements were eased in Italy on 4 May, which led to a flood of people returning to parks.

France eased restrictions on 1 May, and the UK eased up slightly on 13 May, allowing people to sit down in public places so long as they remain socially distanced.

Other countries have seen park attendance rise without major easing of lockdown – including Canada, Spain, and the US (although states there have individual rules and some have eased restrictions).

In some countries, people never really stopped going to parks.

Authorities in the Netherlands and Germany were not as strict as other countries about their citizens visiting local parks during lockdown, while Sweden has famously been avoiding placing many restrictions on people’s daily lives.


There is a growing body of evidence to suggest that access to green space has major benefits for public health.

A recent study by researchers at the University of Exeter found that spending time in the garden is linked to similar benefits for health and wellbeing as living in wealthy areas.

People with access to a private garden also had higher psychological wellbeing, and those with an outdoor space such as a yard were more likely to meet physical activity guidelines than those without access to outdoor space. 

Separate UK research has found that living with a regular view of a green space provides health benefits worth £300 per person per year.

Access is not shared equally, however, which has important implications for equality under lockdown, and the spread of disease.

Statistics from the UK show that one in eight households has no garden, making access to parks more important.

There is a geographic inequality here. Londoners, who have the least access to private gardens, are most likely to rely on their local park for green space, and have the best access to parks. 

However the high population in the capital means that on the whole, green space per person is lower – an issue for people living in densely populated cities everywhere.

There is also an occupational inequality.

Those on low pay – including in what are statistically classed as “semi-skilled” and “unskilled” manual occupations, casual workers and those who are unemployed – are almost three times as likely as those in managerial, administrative, professional occupations to be without a garden, meaning they rely more heavily on their local park.

Britain’s parks and fields are also at significant risk of development, according to new research by the Fields in Trust charity, which shows the number of people living further than a 10-minute walk from a public park rising by 5% over the next five years. That loss of green spaces is likely to impact disadvantaged communities the most, the researchers say.

This is borne out by looking at the parts of the country that have private gardens.

The least deprived areas have the largest gardens

Though the relationship is not crystal clear, it shows at the top end: Those living in the least deprived areas have the largest private green space.

Although the risk of catching coronavirus is lower outdoors, spending time in parks among other people is undoubtedly more risky when it comes to transmitting or catching the virus than spending time in your own outdoor space. 

Access to green space is therefore another example – along with the ability to work from home and death rates – of how the burden of the pandemic has not been equally shouldered by all.

Michael Goodier is a data reporter at New Statesman Media Group, and Josh Rayman is a graphics and data visualisation developer at New Statesman Media Group.