‘The contribution of complex trauma to psychopathology and cognitive deficits’ – In conversation Dr. Stephanie Lewis

Avatar photo
You can listen to this podcast directly on our website or on the following platforms; SoundCloud, iTunes, Spotify, CastBox, Deezer, Google Podcasts, Podcastaddict, JioSaavn, Listen notes, Radio Public, and Radio.com (not available in the EU).

Posted on

In this podcast we talk to Dr. Stephanie Lewis, Editor of The Bridge, and Clinical Lecturer in Child and Adolescent Psychiatry at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London.

The main conversation is around complex trauma and Stephanie’s paper that was recently published in the British Journal of Psychiatry, ‘Unravelling the contribution of complex trauma to psychopathology and cognitive deficits: a cohort study’. Stephanie discusses the gaps in the literature that made it important to explore complex trauma, the methodology, and headline findings from this study.

Stephanie highlights that the usual approach to trauma research and clinical practice, which considers all traumas together, has probably underestimated the mental health difficulties experienced by people who have been exposed to complex types of trauma.

We also hear about her plans to find out which aspects of complex trauma are important, and really understand whether complex trauma leads to qualitative difference in mental health problems.

Please subscribe and rate our podcast from your preferred streaming platform, including; SoundCloudiTunesSpotifyCastBoxDeezerGoogle Podcasts and Radio.com (not available in the EU).

Dr. Stephanie Lewis

Dr. Stephanie Lewis is a Clinical Lecturer in Child and Adolescent Psychiatry at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London. She studied medicine at Imperial College London, and since graduating has undertaken integrated clinical and academic training, including psychiatry training at South London and Maudsley NHS Foundation Trust and the IoPPN. She is currently undertaking an MRC Clinical Research Training Fellowship, and continues to work as a psychiatrist in child and adolescent mental health services.


Interviewer: Hello and welcome to the In-Conversation podcast series for the Association for Child and Adolescent Mental Health or ACAMH for short. I’m Jo Carlowe, a freelance journalist with a specialism in psychology Today I’m interviewing Dr Steph Lewis, Clinical Research training fellow at the Institute of Psychiatry, Psychology and Neuroscience, king’s College London. Steph’s research focuses on trauma and related mental health problems in young people. She discussed her work on complex trauma at ACAMH’s Emmanuel Miller Conference last year and in a British Journal of Psychiatry paper recently.

We’ll talk more about this topic of complex trauma today. If you’re a fan of our In-Conversation series, please subscribe on iTunes or your preferred streaming platform. Let us know how we did with a rating or review and do share with friends and colleagues. Hi, Steph thank you for joining me. Can you start with an introduction?

Dr. Stephanie Lewis: Yes, thanks very much, Jo. So I am a psychiatrist working with children and young people and I’m also a researcher, and as you mentioned my research focuses on understanding the mental health difficulties experienced by young people who’ve been exposed to traumatic events, and in particular I’ve been recently focussing on a particular type of trauma called complex trauma.

Interviewer: We’re going to look at your paper unravelling the contribution of complex trauma to psychopathology and cognitive deficits, a cohort study, but before we go into depth I think it would be really helpful if you can explain the difference between complex and non-complex trauma.

Dr. Stephanie Lewis: Yeah, I think that’s a really important place to start, actually, Jo, because these different terms that we use have been used in different ways with different meanings. So it can get quite confusing, and actually I think maybe the most helpful term to describe first is trauma itself. So when I talk about trauma in this podcast I’ll be describing the exposures. These are defined clinically as events that involve actual or threatened death, serious injury or sexual violation.

So this covers a wide range of experiences and when this clinical definition was first, sort of, developed in the late 1970s, early 1980s, it was thought that or it was assumed that all types of trauma were linked with the same type of mental illness and the focus then was on post-traumatic stress disorder, PTSD, which had just been newly defined, but about a decade later a group of trauma experts who got together to regularly discuss their clinical work, they noticed that some of their patients presented quite differently to others.

And these patients had experienced types of trauma that have been called complex traumas. So these traumas are characterised by including multiple events that were interpersonal in nature. So that’s where one person intentionally harms another person, and these traumas occurred in childhood or adolescence. Complex traumas include experiences like repeated child abuse and based on their observations of these patients, those experts hypothesised that complex trauma might lead to more severe mental illness, including both broad mental health problems and potentially also cognitive deficits and that’s compared to other types of trauma, which we call non-complex trauma that might involve non-interpersonal traumas like car accidents or natural disasters or single events, if that makes sense.

Interviewer: So it seems a personal aspect of it that’s really significant.

Dr. Stephanie Lewis: That’s one of the aspects that’s really important, the interpersonal aspect and also the fact traumas are kind multiple times, and particularly it’s thought to be important that these traumas occur in childhood when people that experience the events are developing, potentially these traumas could impact that development. So that’s why it’s thought to be particularly important. So all of these different factors when they occur together we call that complex trauma.

Interviewer: Just to clarify where PTSD comes into it in terms of that being complex or non-complex.

Dr. Stephanie Lewis: Good question, Jo. So when we talk about trauma and complex trauma, we’re talking about the exposure. So that’s the event that happened. So it might be the car accident or the abuse that someone experienced. Post-Traumatic stress disorder, PTSD describes a particular type of mental health problem that can happen after these events. So not everybody who’s exposed to a trauma goes on to develop these sorts of mental health problems but some do. So PTSD was the sort of first defined trauma related disorder. As I say, I think was 1980 that it was first introduced into our diagnostic systems, and the focus in the literature has largely been on PTSD, but the work that we’re doing has shown that actually trauma is related to much broader difficulties. Does that make sense?

Interviewer: Yes, yes, I think it does. I’m just trying to work out whether repeated trauma then can lead to PTSD.

Dr. Stephanie Lewis: So it certainly can, and in fact we know from studies of PTSD that different types of trauma confer a different risk for PTSD when you look at PTSD alone. So I’ve done some research which has found that the interpersonal nature is particularly important and leads to higher rates of PTSD, but it’s really difficult to untangle which aspects of the trauma is the most important, particularly in regards to complex trauma, whether it is the interpersonal aspect, the repeated aspect or the childhood aspect, and this is certainly something I would like to study in future, but that’s a really good question, Jo.

Interviewer: Great. That’s really helpful just to get a sort of background of it. Let’s return to your paper recently published in the British Journal of Psychiatry. Can you give us a summary of what you looked at?

Dr. Stephanie Lewis: Yes, sure. So along with an excellent team of researchers. So this includes Professor Andrea Danese and Keriston Codan and several other brilliant researchers. We investigated the mental health problems and cognitive function, cognitive deficits in a large nationally representative sample of young people. So this is a cohort of over 2000 young people born in England and Wales in 1994 and ’95 who have been followed up throughout childhood and adolescence and assessed most recently at age 18, and this study is called the E-Risk, Environmental Risk Longitudinal Twin Study.

So we looked at the study members and at age 18 we asked them about their trauma exposure in their lifetime, and we looked at their mental health and their cognitive function at that age. So we first found that these young people in our sample who’d been exposed to complex types of trauma had more severe mental health problems and cognitive deficits compared not only to trauma unexposed peers, but also compared to those who’d been exposed to other types of long, complex trauma.

And these difficulties were seen across several mental health disorders and different cognitive domains. So this really provides the most comprehensive evidence to support that hypothesis that I described earlier, that those in the 1980s, 1990s, the experts had made clinical observations to suggest that this might be the case, and now we have really good evidence looking at that.

Interviewer: Steph, what gaps were there in the literature that made it important to explore complex trauma in a population study?

Dr. Stephanie Lewis: It’s really interesting, actually, Jo, because this topic of complex trauma, although, as I mentioned, it was sort of first discussed in the late 1980s, early 1990s it has become particularly popular in recent years and is discussed quite widely by some in clinical practice, but interestingly there’s not a great deal of empirical research testing these theories and hypothesis. There has been a small amount of work that’s compared complex and non-complex, complex traumas but this work has tended to use convenient samples, so unlike our research, they’re not representative of the populations.

It’s difficult to know if the findings generalise to the population. They also tend to focus on a relatively limited range of outcomes. So often the focus tends to be a new disorder called complex PTSD. So researchers tend to look at one outcome, but it hadn’t assessed a broader range of difficulties or cognitive abilities as well, and importantly, the research on this topic has been cross-sectional. So looking at a particular sample at one point in time, which is after trauma exposure and from these studies it’s really difficult to know the order of what came first and what came next.

Really difficult to draw conclusions about whether trauma caused these difficulties or not. Our study sort of addresses all of those three things. We used a representative sample. We looked at broad difficulties and we used a longitudinal design.

Interviewer: You touched on this before, but what were the headline findings?

Dr. Stephanie Lewis: We sort of had two headline findings. I’d really like to highlight today. So the first one is the one that I mentioned before, that young people who had been exposed to complex trauma had more severe mental health problems and cognitive impairments compared not only to those who hadn’t been exposed to trauma, but also compared to their peers who’d been exposed to other types of trauma. So non-complex traumas. So it’s really showing us the difficulties experienced by young people exposed to complex trauma are particularly severe.

The second point I wanted to highlight because we wanted to understand those underlying mechanisms. So when people think about trauma and mental health difficulties a common assumption that’s made is that the trauma has caused those difficulties, but there are alternative possibilities. So it’s possible that people who have vulnerabilities that increase their risk for exposure to trauma and think particularly about complex trauma, those same vulnerabilities might also increase their risk of experiencing mental illness, and that would give an association between trauma and mental illness, even though trauma doesn’t cause mental illness.

That’s a process called confounding. So we really wanted to understand whether these pre-existing vulnerabilities have a role. So this is what we studied next. It was possible to do this in the ERA Study because it’s a longitudinal study, as I mentioned. So we have really early childhood measures. So we looked at a range of potential pre-existing vulnerabilities, things like children’s internalising and externalising symptoms at age five, their IQ at that age as well, the socioeconomic status of their family at that time, and the proportion of their family members who had a history of mental illness.

So we looked at all of those at age five, and interestingly we found that most of these factors were associated with the later exposure to complex trauma, but not non-complex trauma. So this tells us that vulnerable young people are more likely to experience complex trauma, whereas non-complex trauma tends to occur more randomly in the population. We then looked at whether these vulnerabilities might account for the mental health problems and the cognitive deficits that we saw in the groups when we looked at their age 18 findings.

And we found that these vulnerabilities did largely explain the associations between complex trauma exposure and cognitive impairments. So these cognitive impairments include, for example, having a lower IQ, having poorer executive function. Actually, we found that these cognitive impairments didn’t seem to be caused by the trauma, but rather it seemed more likely that these pre-existing vulnerabilities explain those difficulties that we found in people who had been exposed to complex trauma.

Interviewer: What are the implications then for child and adolescent mental health professionals?

Dr. Stephanie Lewis: So I think there are a number of things that it’s important to highlight. Our findings show that the usual approach to trauma research and clinical practice, which considers all traumas together, has probably underestimated the mental health difficulties experienced by people who have been exposed to complex types of trauma. So these findings should really make clinicians aware that it’s really important to undertake comprehensive assessments to better recognise potentially broad difficulties which all need to be considered in a thorough care plan.

And the second finding that I mentioned highlights that not all difficulties experienced by people who’ve been exposed to complex trauma unnecessarily caused by the exposure and that pre-existing vulnerabilities that increase the risk of complex trauma also seem to be responsible for cognitive impairments, and that’s really important to consider, and clinicians should avoid making causal assumptions in their formulations when we find difficulties in young people, and that’s really important because it might affect how the approach that we take to managing these difficulties and the recommendations we make and these pre-existing vulnerabilities should be addressed in management plans too.

Interviewer: How can professionals kind of unpick that then, the formal effect aspect of it?

Dr. Stephanie Lewis: It’s tough. I think it’s really important to understand, to get a timeline for difficulties and also understand what difficulties seem to run in the family. So it might be that if you ask about the difficulties that the young person experienced before the trauma you might find that some of the problems were there before or might run in the family. It’s actually really important to bear that in mind because some of those factors might actually be complicating factors that prevent young people getting the best benefit out of treatment. So it’s important that we identify that early and consider it in management plan.

I’m just wondering what the implications are for children and families themselves. You know, if there are pre-existing vulnerabilities. There may be an assumption that complex trauma will be the, sort of, trajectory for that child.

Yeah, I mean, one thing that’s really important to mention is that, I know we touched on this earlier, but just to reiterate, I guess not every child who has these vulnerabilities will go on to experience complex trauma and not every child who experiences complex trauma will go on to have mental health and cognitive difficulties. So it’s really important to understand these difficulties because they might point us towards understanding the mechanisms that lead to later difficulties, and when we understand that or we understand who’s at greatest risk that might help us to develop prevention strategies that are targeted to those at high risk.

These are really important areas for future research and highlights several factors that might be good targets for those intervention strategies and prevention strategies.

Interviewer: Steph, what message should policy-makers take from your findings?

Dr. Stephanie Lewis: I think that’s a really important question. I think that really our findings highlight the burden of mental health problems experienced by young people who’ve been exposed to trauma and especially complex trauma. So therefore a really important need to ensure that there’s adequate care available to address the often high needs of young people who’ve had these experiences.

Interviewer: Is there anything else that you want to highlight from this research?

Dr. Stephanie Lewis: Yes. So I think one thing that I may be missed describing earlier was that although early vulnerabilities seem to account for the cognitive deficits we found, they don’t seem to account for or they don’t fully account for the mental health difficulties that we found in young people who’d been exposed to complex trauma. So it is possible that experiencing complex trauma might give rise to these difficulties, and that’s a really important area to understand and research in future. The second point that I wanted to raise is to highlight that the findings with respect to non-complex trauma.

So we compared three groups. Those exposed to complex trauma, non-complex trauma and no trauma, and although those exposed to non-complex trauma had less severe mental illness than those exposed to complex trauma, the non-complex trauma group still had more severe mental health problems than the no trauma group. So there’s still a really important group to be aware of and really interestingly, the difficulties were also relatively broad. They weren’t limited to PTSD, as some might hypothesis that they might be. They experienced a broad range of those difficulties, although they didn’t experience any cognitive deficits that we found.

Interviewer: Are you planning some follow-up research that you can reveal to us?

Dr. Stephanie Lewis: I’d really like to better understand which aspects of complex trauma are important. So those, sort of, early questions that you raised Jo I think they’re really important questions to study next and to really understand whether complex trauma leads to qualitative difference in mental health problems, so that it’s when all those features come together. The combination is important of having multiple interpersonal difficulties during childhood or whether it’s more of a quantitative effect in that complex trauma maybe represents the upper end of a continuum or several different continuums where perhaps due to the multiple nature of events frequency or the severity of events to really understand which of those aspects are more important if that’s the case.

Interviewer: Finally, Steph, what’s your takeaway message for those listening to our conversation?

Dr. Stephanie Lewis: Really, that not all traumas are the same. Complex traumas are more strongly linked to a broad range of difficulties, and that it’s really important that these difficulties are identified and considered in care planning.

Interviewer: Steph, thank you so much. For more details on Dr Steph Lewis visit the ACAMH website, www.acamh.org and Twitter at ACAMH. ACAMH is spelt ACAMH, and don’t forget to follow us on iTunes or your preferred streaming platform. Let us know if you enjoyed the podcast with a rating or review and do share with friends and colleagues.


Thank you for sharing. Quite helpful information.

Add a comment

Your email address will not be published. Required fields are marked *