Guest post: Autistic traits in children with ADHD: a marker of severity?

25 April 2013 by Pete Etchells, posted in Autism, Guest post, Research news

Today's post was written by Joanna Martin. Joanna is a 2nd year PhD student at Cardiff University, in the Institute of Psychological Medicine and Clinical Neurosciences. For her undergraduate degree, she studied Experimental Psychology at Bristol University. 

She's on Twitter as @trufflesquirrel and blogs about life as a PhD student at:


The way researchers, clinicians and society think about child mental health problems is constantly evolving as we discover and come to understand more about the nature of human mental health. This is a particularly topical issue with the forthcoming release of the DSM-5, the latest version of the Diagnostic and Statistical Manual, which is a book used by psychiatrists to diagnose mental health problems across the lifespan. One fairly subtle change which we can expect to see is the removal of a restriction under attention deficit hyperactivity disorder (ADHD). Under the current version of the manual (the DSM-IV), ADHD cannot be diagnosed in the presence of a pervasive developmental disorder (which is an umbrella term for autism spectrum disorder (ASD) and related conditions like Rett’s syndrome).

Why this restriction was in there in the first place is not entirely clear, except that it was assumed that if a child has ASD, their social and communication deficits and stereotyped behaviours somehow account for any problems they might show with hyperactivity, impulsivity or attention. The difficulty with such a restriction is that the children with ASD who do have problems with hyperactivity, impulsivity or attention might not get any treatment for these, if they were not also diagnosed with ADHD. Unlike with ASD, medications (particularly stimulants, like the well-known Ritalin) are actually frequently quite effective in lessening the behavioural and attention difficulties associated with ADHD. So being able to diagnose and treat both problems should be a change for the good.

Indeed, the rate of ADHD problems in children with ASD and vice versa is a lot higher than just the rate of ADHD or ASD in the general population. But because of the restriction under DSM-IV, so far not a huge amount of research has gone into trying to understand the relationship between these different but co-occurring conditions.

I chose to study this topic for my PhD, in the hope that I could learn more about children who have both ADHD and ASD problems. I started by looking at a large sample of children who had been diagnosed with ADHD, which had been recruited from around the UK (mostly Wales) over a number of years (see here for some background information on the study). In fact, before I started my PhD, I helped to collect data from some of the final families to take part in this study. Parents completed a fairly lengthy interview about their children’s ADHD problems and also about other difficulties, namely behavioural problems (such as stealing or fighting), anxiety (for example fear of separation from parents) and depression (for example low mood or self-harming). Parents also filled out some questionnaires, including the Social Communication Questionnaire, which asked 40 questions about autistic traits, and others which asked about children’s language and motor abilities (such as when they started walking and talking). Meanwhile, the children completed a battery of tests, including an IQ test to assess cognitive abilities and some reading and spelling tests.

Unlike in many studies researching ADHD and ASD, we did not collect data from typically developing children. This is mostly because the sample was recruited for a genetic study of ADHD and we already had control genetic data from the population (thanks to an international collaboration with other researchers). However, given the amount of information collected, the sample provides us with exciting opportunities to address many other interesting questions too. So instead of comparing the children with ADHD to their typical peers and looking for group differences, we looked at variation within the ADHD sample. In total, there were 711 children whose parents completed enough of the interview and questionnaires for us to be able to analyse the data they provided.

What we found is that the more autistic traits children had, the more severe their ADHD symptoms were. What’s more, even after accounting for how severe their ADHD was, more autistic traits predicted more anxiety and behavioural problems, as well as more cognitive difficulties (particularly working memory problems) and a greater chance of having language and motor delays. There was no relationship between autistic traits and reading or spelling abilities in these children with ADHD. Although autistic traits also predicted more depressive symptoms, these were actually accounted for by the greater rate of ADHD symptoms (that is, more severe ADHD predicted worse depression symptoms and so autistic traits only really predicted more depression by virtue of being related to ADHD severity).

One important point to mention about the study is that although we looked across a wide range of ages (from 5-18 years) we can’t draw any conclusions about cause and effect because we looked cross-sectionally (that is, only at a single time point in each child’s life and not across time). Also, although we found a general pattern that more autistic traits indicated more of the other problems, not all children who had autistic traits had these other difficulties.

Based on these results, we concluded that it is important for clinicians assessing and diagnosing a child with ADHD to also be actively aware of the child’s social and communication abilities and to determine whether they display any stereotyped or repetitive behaviours. The presence of such autistic traits may be a marker of greater symptom severity and possibly additional, more complex needs. Our results also support the change in the DSM-5, which will allow a dual diagnosis of ADHD and ASD in a child, hopefully resulting in more research into and support for both sets of problems in children.

This research has been published today in European Child and Adolescent Psychiatry, where I am pleased to say it is available Open Access (a requirement of the Wellcome Trust who funded the study). I will also be presenting it as a poster at the upcoming International Meeting for Autism Research next week (poster session on May 4th). As my PhD continues, I hope to find out more about how ADHD and autistic traits relate to one another and what the common risk factors for these problems might be.



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