Professor Helen Minnis and Lisa Dinkler discuss their paper “Maltreatment-associated neurodevelopmental disorders: a co-twin control analysis” published in the Journal of Child Psychology and Psychiatry.
Professor Helen Minnis: Hi, I’m Helen Minnis and this is Lisa Dinkler, and we’d like to talk about a paper that we just had published in the JCPP called ‘Maltreatment Associated New Developmental Disorders, a co-twin control analysis’, because we think its got some quite important clinical implications, but it’s a bit complicated to describe the methodology.
So, really just to start off, I got interested in this because I’d noticed in my clinical practice and in my research that you would occasionally meet maltreated children who had really a lot of neurodevelopmental or psychiatric problems. So, I’ve met children who had six or seven different diagnosis and I thought really is this real, and are these children more likely to have lots of problems? So, we decided to have a look at this in a population context, and I got in touch with colleagues in Sweden who work with the CATSS Study. So, do you want to tell us a bit about the CATSS Study Lisa?
Lisa Dinkler: Yeah, sure. The CATSS is the Child and Adolescent Twin Study in Sweden and it’s an ongoing longitudinal study, which is aiming to include all twins born in Sweden since first of July nineteen ninety two. So, parents are contacted when the twins turn nine years old and they are asked to participate in a telephone interview. In this interview, it is assessed for neurodevelopmental problems with the A-TAC. The A-TAC is the Autism-Tics, ADHD and other Comorbidities inventory, which is a very well validated instrument with psychometric properties that are excellent to screen for ADHD and autism, for example. So, in our study, we looked at ADHD, autism, learning disorders and tic disorders in about eight thousand twins, and we were interested in the number of these neurodevelopmental problems they had.
Professor Helen Minnis: So, in other words, our first question was, “Is there an increased number of neurodevelopmental disorders in maltreated children compared to children from the general population? So, in other words do they have an increased neurodevelopmental load? And we found that they do.
Lisa Dinkler: Yeah, that is what we found, that maltreated children have on average more neurodevelopmental problems than the non-maltreated ones, and in fact, maltreated children had a six times higher risk to have three or more neurodevelopmental problems if compared to the non-maltreated children.
Professor Helen Minnis: So, in other words, my, kind of, clinic impression was correct. They were likely to have more. I guess, then, the next question was, “Does the maltreatment cause this?” and I suppose that could have came about because in, for example, studies of institutionalised children, we know that they are at higher risk of having ADHD, for example, and so there’s always been a kind of question around about whether there’s another route into ADHD or other neurodevelopmental disorders. In other words, does maltreatment cause it? So, we used the co-twin control design. Could you explain that?
Lisa Dinkler: Yeah. The co-twin control method is designed to investigate causal effects in observational research. So, basically, it can tell us if an association is consistent with the causal effect or if it is better explained by familiar factors, which would be genetic factors and common environmental factors. So, basically, what we do is to take identical twins, which are matched for their genetics because they share a hundred percent of their genes, and they are also matched for their common environment because they are raised in the same family. If we then take an identical twin pair, where one twin has been maltreated and the other one hasn’t, and we look at their outcome in terms of neurodevelopmental problems. Then we can see if there is a difference in the outcome. Then the maltreatment which they were discordant for is responsible for that because we controlled for genetic factors and the common environment.
Professor Helen Minnis: So, just to get it clear in my mind, then, if we have maltreated children, sorry, if we have identical twins who are discordant for maltreatment, who differ in whether they have been maltreated or not, and they actually then have similar numbers of neurodevelopmental disorders. Then it’s very likely that the maltreatment has not caused the increased neurodevelopmental load, and that’s what we found isn’t it? We found that actually it appeared that maltreatment wasn’t causing this increase neurodevelopmental complexity.
Lisa Dinkler: That’s correct, yeah.
Professor Helen Minnis: And so we then wanted to look at individual disorders, so ADHD, ASD, etc, and we found a slight increase in symptoms of those individual disorders associated with maltreatment.
Lisa Dinkler: Yes, exactly. We found that maltreatment was associated with a small increase in symptoms of ADHD and autism. But that means that the maltreatment could either cause that these symptoms are increased, but it could also mean that children with more symptoms are more likely to be maltreated.
Professor Helen Minnis: So, it could go either way. So, we actually don’t know which is the direction it goes out to. So, in other words, it could be that being maltreated makes you more likely to have worst ADHD, if you’ve got ADHD, or it could be if your ADHD is worst, you’re more likely to be maltreated.
Lisa Dinkler: Yeah, precisely.
Professor Helen Minnis: So, I think these findings have got really important clinical implications, because, you know, in Scotland, anyway, my impression is that maltreated children are less likely to be assessed for neurodevelopmental disorders, because we assume that the behavioural problems are just, you know, explicable by the maltreatment. Whereas what we are actually saying is that children who have been maltreated must be assessed. They must have a detailed assessment for neurodevelopmental disorders, because they’re more likely to have neurodevelopmental disorders and they’re more likely to have more neurodevelopmental disorders.
Lisa Dinkler: Yeah.
Professor Helen Minnis: So, a, kind of, linked thing is that if children have complex neurodevelopmental disorders, there’s a possibility, we can’t prove this in this study, but there’s a possibility that they might be at higher risk of being maltreated. So, we need to watch for that as well. And then I think the third really important implication, for me, is this idea of trauma related disorders, which are talked about right across the lifespan, and it means that even in adults, if they’ve got what we traditionally call a trauma related disorder, we should be assessing for neurodevelopmental disorders, because that child or adult could have ADHD or autism.
Lisa Dinkler: Yes, that is very important.
Professor Helen Minnis: Thank you very much Lisa.
Lisa Dinkler: Thank you very much.