Refugees from Idlib fleeing the Syrian Civil War in a camp in the Bekaa Valley of Lebanon. Credit: DFID – UK Department for International Development, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons.

The Syrian civil war began in 2011 and has led to the deaths of an estimated 600,000 people, including many children. Although technically ongoing, the peak of the violence in the mid-2010s led to more than 6.7 million Syrians fleeing their country. Many became refugees in Middle Eastern countries such as Lebanon, Turkey, Egypt, Iraq and Jordan, whilst close to a million remain in Germany.

The bitter fighting had many casualties, not least millions of displaced children, but the refugee settlements in Lebanon’s Bekaa Valley provided an opportunity for a study into the impact of war on children. Professor Michael Pluess, then of Queen Mary University London, but now at the University of Surrey, undertook groundbreaking research which concluded children living in war-torn countries not only suffer from poor mental health outcomes, but that war may cause adverse biological changes at the DNA level, which could have lifelong health impacts.

ScienceVega caught up with Professor Pluess to discuss this research and found out just how impacted children can be by the horrors of war.    

ScienceVega: What led you to undertake this particular research?

MP: This is part of a bigger project that I developed in 2013 when the refugee crisis in Syria started to emerge. It was a huge issue, especially in Germany in 2015 when around a million Syrian refugees were invited to settle, and there were a lot of concerns raised. It was the biggest refugee crisis for a very long time.

I was speaking to a friend of mine who was involved in an NGO dealing with the refugee situation in Lebanon and he asked me whether I had any ideas to do some research with them. Based on that, I developed the initial idea that I would do some research on the most vulnerable children in this world, which became a project focused on resilience. I particularly wanted to understand individual differences in how children respond to the experience of war and displacement. Ultimately I got the funding to run this large study with Syrian refugees in Lebanon.

We were particularly interested in the biological pathways involved in both risk and resilience: Why do some children develop mental health problems when they experience war and others don’t? What are the biological factors involved in that?

We set up a large study called the BIOPATH study with 1,600 families, and for each family a child and the primary caregiver would participate in the study over a period of one year. We had two data points at times of data collection, the first one at the end of 2017 and then a year later when we collected additional data from the same sample. We also ran a clinical trial where we provided psychotherapy to these children, which we did over the telephone.

The basic aim was to understand the effects of war on children with a specific focus on individual differences and the biological mechanisms involved in that.

ScienceVega: Can you describe the process which led to these results?

MP: We were working with local psychiatrists and local researchers in Lebanon as well as with an NGO who were working with communities of Syrian refugees. We focused on a specific area in Lebanon, which had the more vulnerable Syrian refugees living there. We worked with almost 80 different refugee settlements in the Bekaa Valley area of Lebanon. We went into those communities, we told people about the study, and asked them whether they would like to participate. If they did, we asked both caregiver and child to complete a questionnaire and we obtained a hair and saliva sample from the child. From the saliva sample we extracted the DNA and then analysed it for DNA methylation.

Azaz, Syria during the Syrian civil war. 16 August 2012, Azaz residents pick up after aerial bombings. Bombed out buildings. Credit: Voice of America News: Scott Bob report from Azaz, Syria, Public domain, via Wikimedia Commons.

ScienceVega: Why is this research ‘groundbreaking’?

MP: With this particular paper where we are looking at the DNA methylation, which is an epigenetic mechanism that influences gene expression, in order to find out how environment factors can influence what genes are active or passive. In the social sciences or in psychology and psychiatry, it is a relatively new focus to look at the effects of traumatic experiences at the molecular level.

It hasn’t been done in a refugee population of that size yet, because it’s very difficult to do research in humanitarian settings. Therefore our study is one of very few of this size that are longitudinal, are reaching children from a wide range and includes biological markers such as DNA methylation. We also have genetic and hormonal data. That makes the study rather unique and it was the largest study so far looking at how war exposure is associated with DNA methylation across the whole genome.

Previously other research looking at epigenetic modifications in relation to trauma focused on a small number of genes that are associated with stress response. But we applied an epigenome-wide approach where we looked at hundreds of thousands of different locations across the chromosome. It’s a unique sample, it’s a unique context and it’s a unique methodological design given the sample size.

ScienceVega: How do boys and girls differ in the results?

MP: We looked at whether different aspects of war exposure are associated with changes in DNA methylation and we did find some specific DNA methylation differences for girls and for boys.

In both we found that higher war exposure was associated with differences in DNA methylation. Whilst the DNA doesn’t change, DNA methylation means that methyl groups bind to the DNA in specific locations. If a methyl group binds to the DNA, it basically mutes that section of the gene so it’s not being used. We saw some increased methylation and some decreased methylation in response to war, and we generally found that across the whole sample.

However there are also some specific DNA methylation locations that differ from girls to boys.

ScienceVega: How could these changes manifest themselves in later life?

MP: Mental health is impacted by war exposure. We know that from our other analyses in the same sample. These DNA methylation locations are associated with specific biological pathways and biological mechanisms. What we found was that the genes that we identified are associated with some biological mechanisms, such as the transport of neurotransmitters from one neuron to the another. That is associated with neurotransmission and intracellular movements and it might have an impact on brain development, or on the function of the brain.

It’s difficult to say exactly what the biological consequences of these DNA methylations would be, but what we do know is that there are biological consequences from war exposure: how these biological pathways are implicated in later mental health problems, or behavioural problems or perhaps even physical health problems would require additional work.

An ‘informal tented settlement’ in Lebanon’s Bekaa valley. The mountains in the background form the border with Syria, just a few miles away. Millions of Syrian children face their worst winter yet as worsening weather and crowded refugee camps create the ideal conditions for the spread of life-threatening diseases such as pneumonia. The UK will provide winter tents, warm clothing and heaters as part of an allocation of nearly £90 million to help hundreds of thousands of Syrians, especially children, cope with the onset of winter. There are over 800,000 Syrian refugees in Lebanon now – 400,000 of whom are children. Credit: Russell Watkins/Department for International Development, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons.

ScienceVega: Is the research applicable across all kinds of traumatic events, for example witnessing a car crash rather than being in a warzone?

MP: That’s an interesting question. There has been previous research in western populations looking at children that experience trauma to try figure out how this is associated with DNA methylation. Many of them looked at child abuse or childhood maltreatment, and we wanted to see whether any of those findings replicated in our sample.

We tested hundreds of findings that have emerged in other studies in our sample and we found that that hardly any of them replicated. Only two out of 258 previously reported associations were associated with war exposure. This could suggest many things: it could suggest that the findings generally might not be very reliable across all these different studies that look at DNA methylation, but it could also mean that the DNA methylation changes that we see in relation to war exposure are different from that those that we see with early childhood maltreatment or traumatic events such as accidents.

What we know today, is that it seems that different trauma seems to have a different effect on DNA methylation.

ScienceVega: Are there any practical solutions that this research could lead to in terms of limiting the effect of war on children?

MP: What it tells us is that war exposure is not just an experience that you have and then perhaps you get over it. It can actually have biological implications in that it changes how the DNA works in a human being, which will have an impact on development across life. It further emphasises the need to protect children from war exposure and displacement.

What also needs to be looked at is how stable are these changes. Do we still see them when those children are 50 years of age? DNA methylation can change, so perhaps if these children get the right kind of support, or they’re being moved out of the context associated with the trauma, will we see that reflected in a reversal of DNA methylation changes.

When we look at epigenetic ageing, a biological indicator of the ageing process, we usually find that adults are biologically older than their chronological age if they experienced trauma. This has mostly been looked at in older adults but we applied a range of epigenetic clocks in our sample to see how war exposure is associated with biological ageing measured with DNA methylation. We expected that biological ageing would be accelerated because that’s what we usually find in adults. But we found the opposite; we found that for children with higher war exposure their biological ageing was slowed down. Obviously in children, we don’t necessarily see an ageing process in the sense of a loss of function, but we see the development, which is the growth of function.

What our findings suggest, and it’s a novel finding, is that war exposure might slow down the development of these children, which means it could lead to developmental delays. This is something that would need to be investigated further.

These children experienced war exposure between one and four years prior to our data collection. So an important question to consider is, are these developmental delays sustained? For example, will these children struggle in school because their brains may not have developed as quickly as those of children that have not been exposed to those kinds of experiences?

The impact in development is quite a significant and interesting finding. There could be all sorts of knock-on effects that are caused initially by war exposure and the biological pathways that are associated with reduced or slower development. This could also explain why these children might be struggling longer term, because we do know there’s some research suggesting that early trauma exposure can have long-lasting effects on children’s lives.

Muhanad*, aged 11, from Syria, in school in Lebanon’s Bekaa Valley, close to the border with Syria. UK aid is supporting NGOs including Save the Children and UNICEF to provide catch-up education to thousands of Syria’s children. Many of them have missed more than a year of school due to the conflict, and getting them back into education is crucial to preventing them becoming a lost generation. Picture: Russell Watkins/Department for International Development *Name has been changed Credit: DFID – UK Department for International Development, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons.

ScienceVega: What follow up research would you like to see given these results?

MP: Much of the research on refugee children is cross-sectional, like a snapshot at one time point where we collect data on war exposure, or exposure to other traumatic experiences, and we don’t really know how things develop over time.

We really need longer studies that are longitudinal and track a child throughout development. There are very few studies that do that, particularly studies that collect data in a humanitarian setting, because it’s very difficult to keep people in the same study when they move around.

But that is what we need to understand: how long lasting are those effects, and what can we do to prevent those effects from having a long-lasting impact on these children? We do have a wide range of ages in our sample, so we can look at some of those questions.

The next thing that we want to do, because we have all the data we are currently looking at, is the impact of war on other biological markers such as telomeres, which again has to do with biological ageing. We are also looking at the impact of nurturing experiences on DNA methylation.

A few years ago we published a theoretical model on the epigenetics of psychological resilience and that model includes various aspects that could have an influence on epidemic mechanisms, including DNA methylation that is being transmitted to the next generation. Therefore some of these children might have inherited some of the DNA methylation because of the trauma exposure from a person of a previous generation. That could mean DNA methylation will build up over time in response to the quality of their environment. These are important things that require longitudinal and multi-generational studies.

But much research has focused on the negative impact of negative experiences on DNA methylation. We also want to look at positive experiences. For example, with a child that has a particularly supportive parent, do we see an impact on that on their DNA methylation as well?

ScienceVega: How difficult is it to work with children on something like this?

MP: It’s important to stress the ethical aspects of doing research with vulnerable children in such extreme circumstances. Many of the children in our study had no access to school and experienced significant deprivation. Therefore, we offered free mental health services to everyone that participated in our study.

The study was conducted to an ethically very high standard and participation was completely voluntary. It was a study that many thought would not be possible to do and it was indeed extremely difficult. We worked with the government in Lebanon and we worked with many other NGOs and local stakeholders.

The research suggests that there is a heavy burden of war exposure and displacement on the children of our study. For example, every second child in our sample met the criteria for a clinical mental health disorder and many of those children don’t get the support that they need.

We hope this study, and some of the other work we have done, highlights the importance of providing support to these children because they often have no voice and very little research is focused on children in humanitarian contexts.

The link to the original paper can be found here.

Portrait credit: Michael Pluess.