We are the Association for Child and Adolescent Mental Health, or ACAMH for short. And this is ACAMH LEARN. Hello, my name is Dr. Tom McAdams. I'm a mental health researcher based at King's College London. My research is focused on understanding how and why mental health problems develop. I'm particularly interested in why mental health problems run in families, so I'm interested in understanding the relative roles of genetic risk versus the family environment. And in recent years, I've become particularly interested in the association between maternal stress during pregnancy and subsequent postnatal outcomes in children. So in particular, the association between maternal mental health during pregnancy and offspring emotional and behavioural problems in childhood. So the idea that emotional distress experienced during pregnancy can have a detrimental effect on the developing foetus has gathered momentum in recent years, so there have been newspaper and magazine articles published on the topic. And a search on the internet will yield countless web pages discussing the idea that emotional distress during pregnancy, so experiences of depression or anxiety or stress can affect the developing foetus in such a way that it influences brain development, and, ultimately, has a causal influence on a child's emotions and behaviour, potentially, many years post-natally. As well as getting increasing amounts of attention within the media, this topic is also captured the imagination of many within the scientific community. So here's just a few examples of some reviews of the literature that demonstrate that there is, indeed, an association between antenatal stress and various postnatal child outcomes. So we know that this idea is something that parents and expectant parents are aware of, and they sometimes worry about. So my team and I, we run a parent engagement project called Family Footsteps. And in this project, we've been speaking with parents who are concerned about mental health within the family. And we've been asking them what questions they have about mental health that they would like answers to. And this is something that has come up repeatedly. People want to know if stress or mental health issues experienced during pregnancy have an effect on their unborn child. So people have been asking us questions, such as, did my stress during my first pregnancy make my first born child more sensitive and more emotional? Did my perinatal depression have a lasting impact on my daughter? And people are letting us know they'd like to know more about the association between perinatal depression and potential impacts on the baby. So this is something that's interesting to lots of people. What do we actually know? Well, we do know that children born to mothers who experience mental health problems during pregnancy are slightly more likely than others to grow up to exhibit behavioural and emotional problems. And the association is not super strong. But there is an association. This still leaves some important questions unanswered, though, because what we really want to know is, does exposure to maternal stress during pregnancy cause these problems to develop? And of course, we all know correlation does not equal causation. We all know this, but I think we're all guilty of occasionally forgetting this fact as well. So how is this relevant to our understanding of the association between maternal emotional distress during pregnancy and child emotional and behavioural issues? Well, if foetal exposure to maternal emotional distress during pregnancy does cause children to exhibit heightened emotional and behavioural problems in childhood, then the process looks something like this. Stress or mental ill health during pregnancy influences foetal development in such a way, and there's lots of theories about how this might happen, but it influences development in such a way that children born of such pregnancies become more likely to experience emotional and behavioural problems post-natally, and as I say, potentially for many years. But are there alternative explanations for this association? And if so, what are they? Well, mental health in response to stressful experiences are genetically influenced traits. So all human traits are to some extent genetically influenced. So whether we're talking about height or eye colour or personality traits or mental health, they're all under genetic influence. And stress, depression, and anxiety during pregnancy, they're no different. Research shows that genetic factors play a role in influencing a person's emotional stress response to pregnancy. This does not mean that genes are the only things that matter when we're talking about stress during pregnancy. Of course, contextual factors are very important as well, but genetic factors do play their role. This is important because, of course, parents pass 50% of their genome onto their child. And the child's genome influences foetal development and postnatal emotional and behavioural characteristics of the child as well. So if some of the genetic factors involved in maternal distress during pregnancy are transmitted to their child, in whom they influence child emotional and behavioural traits in childhood, then this could explain the association between maternal distress during pregnancy and child emotional and behavioural outcomes. Crucially, it could explain the association, even if there's no causal influence of distress during pregnancy on foetal development. What other explanations might there be for this association? Well, as well as genetic influences, parents and children share an environment. They live in the same house, in the same neighbourhood, in the same family. They share the same socioeconomic conditions, they breathe the same air, and they eat the same food. We know that there are many, many environmental influences on mental health. Money troubles, relationship problems, work stress are all known to influence our mental health. So if any of the environmental factors that influence maternal distress during pregnancy, also influence child emotional and behavioural traits post-natally, then this could explain the association between maternal distress during pregnancy and child emotional and behavioural problems? Crucially, again, it could explain the association, even if there's no causal influence of distress during pregnancy on foetal development. What other explanations might there be? Well, we know that maternal distress during pregnancy, it doesn't exist in isolation. Often, it is preceded by signs of stress or anxiety or depression before pregnancy. And after birth, these symptoms can very often persist or recur. So this means that children are typically not exposed to maternal distress during pregnancy exclusively. Rather, such children will also be exposed to parental stress post-natally and into childhood. And of course, if this postnatal exposure has an impact on the development of child emotional or behavioural problems, then it could explain the association between maternal distress during pregnancy and child emotional and behavioural problems in childhood. And again, importantly, it could explain the association, even if there's no causal influence of stress during pregnancy on foetal development. So we've identified three possible alternative explanations for the association between maternal distress during pregnancy and child emotional and behavioural problems in childhood. And these don't involve a causal effect. So these explanations are not mutually exclusive to one another. They could all be happening at the same time. And they could in fact, all be true alongside distress during pregnancy having a causal effect on child emotional and behavioural problems. Now, distinguishing between all of these possible explanations is extremely challenging. And it requires some scientific creativity. So the classic scientific method for identifying whether one thing causes another is, of course, the experiment. But for obvious ethical reasons, we can't create an experiment in which we make some people stress during pregnancy to see what happens to their children. So we can't establish cause and effect in this way with this particular association. So we have to look for naturally occurring situations that help us to distinguish causation from correlation. So I'm going to quickly introduce you to a few scientific methods we use for this purpose. I'm not going to go into great technical detail. I'm going to not give very much technical detail at all, actually. I just want to provide some insight into what we can do to distinguish whether the association between maternal stress during pregnancy, and child emotional and behavioural problems may be a causal one, and/or whether it is attributable to genetic transmission of risk for shared environmental influences or to postnatal effects. And so to do this, we often collect data on families. So not just mother and child, which is, of course, the focus of this, but also on entire nuclear families and even entire extended families as well. So one design we use involves comparing siblings to one another who were exposed to different amounts of maternal stress during pregnancy. If we collect information from hundreds or thousands of families in which moms were more stressed during one pregnancy versus the other, then we can assess whether the children exposed to the greatest stress grow up to exhibit more emotional and behavioural problems than their siblings. If foetal exposure to stress causes the development of emotional or behavioural problems. This should be the case. It's useful to compare siblings to one another. Because siblings share most of the alternative explanations that we've covered for these associations. They are reared in the same home environment, they share the same postnatal environment, and they share DNA. In other words, if sibling differences in exposure to foetal stress predict sibling differences in child emotional and behavioural characteristics, then we can say that exposure to stress during pregnancy predicts problems in children even after accounting for genetic transmission of risk. Shared environmental factors in the postnatal environment. In other words, the associ-- sorry. In other words, the association could well be causal. And if sibling differences in exposure to foetal stress do not predict sibling differences in child emotional and behavioural characteristics, then we can conclude the association is unlikely to be causal, and it must be attributable to one or all of the alternative explanations. So as well as comparing siblings in the offspring generation, we can make comparisons between siblings in the maternal generation as well. A particularly useful comparison is that between genetically identical twins? So when identical twins have children, these children are just as genetically related to their mum's twin, as they are to their own mum. This, of course, is because identical twins share 100% of their DNA. But of course, only their mums provide their prenatal environment, so they're only exposed to their mums stress during pregnancy, not to their aunts, but they're as genetically related to their mum as they are to their aunt. So if associations between mum's stress during pregnancy and child emotional problems are causal, then associations between mum and a child should be stronger than those between mum's twin and a child. If these associations are the same size, this suggests that the association is down to the genetic transmission of risk, and that there is no effect of exposure to stress during pregnancy. So there's many family-based studies that we can use to study whether parent child associations may be causal or not. And I very briefly introduced a couple of those methods. And giving you a flavour of the kind of logic that underlies them. And now, we can have a little look at what they've taught us. My colleagues and I, as well as lots of other researchers who are interested in this topic, we have access to a large birth cohort based in Norway called the Norwegian Mother, Father and Child Cohort Study. This is a huge study. They invited all pregnant women in Norway to enrol in the study over a 10-year period. Data was collected from the 15th week of gestation onward, and it continues today, with the oldest children currently being in their mid-twenties. The youngest are in their mid-teens. And this data set includes over 114,500 children born to over 90,000 women. And we've got data on 75,000 fathers. And in amongst all of this data, there are lots and lots of relatives allowing us to use the methods that I just introduced. Norway is not a huge country. This is a huge data set. And so there's almost no one in the data set that isn't related to somebody else in the data set. So we've got lots of siblings and lots of twins and cousins, and there's all sorts of relatedness in there that allow us to pick apart intergenerational associations and ask, are they potentially causal? Or are they down to shared genetic transmission or shared environmental factors? So in the Norwegian mother, father, and child cohort study, moms during pregnancy were asked to report on their depression, their anxiety and their experiences of stress. And then as their children have grown up, they've repeatedly reported on their child's development, including their emotional and behavioural well-being. This has resulted in huge amounts of data that many researchers have assessed using the methods like those we've discussed. So what have we learned? Well, we've found that there is no evidence to support the notion that exposure to maternal emotional distress during pregnancy has an effect on the developing foetus. And there's no evidence for increased levels of emotional or behavioural problems as a response to foetal stress exposure. What does this mean? Well, I hope it is one less thing for people to worry about during pregnancy. Pregnancy is an inherently stressful period when levels of anxiety and depression can increase markedly, and I hope that the knowledge that these experiences will not have a negative effect on your unborn child is something of a relief. And so my take home message is this-- people should not be told that being stressed, depressed, or anxious during pregnancy will have a detrimental effect on their child's behavioural or emotional development post-natally. To be clear, this does not in any way mean that maternal mental health during pregnancy should be deprioritized. Emotional distress experienced during pregnancy should be taken very seriously. And if it's severe enough, then treatment should be sought. Mental health during pregnancy is important, even if it does not impact the developing baby. Poor mental health during pregnancy can sometimes extend into the postnatal period and beyond. So treatment can reduce the severity and longevity of these symptoms. I mentioned earlier this talk was inspired by questions that parents have asked us during the Family Footsteps project. We plan to produce more talks like this one, addressing such issues as the intergenerational transmission of risk for mental health and various related topics. So if you are interested in this, then keep an eye on our website for more content. And thank you for listening. I hope you found this talk interesting. For those who are interested in a deeper dive into what I have spoken about today, I plan to add more in depth version of this talk in the future, aimed at those interested in more discussion of the methods used and more critical analysis. And in the meantime, here, I highlight a few relevant papers that my colleagues and others have produced in recent years, for those who are interested. Thanks again.