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In children, it is common to observe traits of ADHD such as being easily distracted, blurting out answers in the classroom, always ‘on the go’, and fidgeting a lot. However, there are also children on the other extreme, those who have excellent attention, sit quietly in class, and are well organized with their homework. Are they a mirror-image of ADHD or are they expressing overly controlled and inflexible behaviours?
Picture by Roselyne
Scientists believe that attention-deficit hyperactivity disorder (ADHD) does not exist in an all-or-nothing fashion – where you either have the disorder or not – but on a continuum. Just as we differ in height (from short to tall) or weight (under- to overweight), we differ in attentiveness, impulsiveness and active levels. This is why many of us recognize ADHD traits in ourselves, even though ADHD as a diagnosis only affects around 6% of youth. High extreme ADHD traits at one end of the continuum are well studied (those with a diagnosis) but what about those at the other end of the spectrum – those with “low extreme ADHD traits”?
Mirror image of high ADHD traits?
Low extreme ADHD traits might simply be a mirror image of what we see for high ADHD traits. So instead of the inattention and impulse control problems that we commonly observe, those at the low extreme may be perfectly self-controlled individuals, with excellent attention and impulse control skills. For example, we might expect these to be children who are well-adjusted because they pay good attention to the teacher, are very organized with homework, and able to regulate negative emotions such as anger, which allows them to build a positive family and friendship circle.
Too much of a good thing?
On the other hand, excellent attention skills and impulse control may become maladaptive when one has ‘too much of a good thing’. For instance, the cost of being hyperfocus is the inability to switch attention when necessary, or over controlling of one’s behaviour. Hence, we might expect children at the low extreme to also have problems at school or home, due to not being spontaneous or flexible, overly rigid or inhibited, or inactive.
Twins with low ADHD traits
To investigate whether these extremely low ADHD traits reflect a mirror image of high extreme ADHD traits, or are too much of a good thing, researchers here at the Donders examined data from over 2000 16-year old British twins drawn from the Twins Early Development Study. Here, our data consisted of twins self-rated individual differences of their own ADHD traits, on a scale from low to high.
We found that children with the lowest ADHD traits had the lowest levels of depression and conduct problems. They were also the happiest and most satisfied with their lives, did the best at school, showed the most prosocial behavior, and had the least chaotic home environments. Hence, low extreme ADHD traits appear to be highly positive, adaptive traits, consistent with a mirror image of high extreme ADHD traits.
Nature and nurture
What’s interesting about twin studies is that we can address how heritable certain traits are. We know that ADHD is one of the most highly heritable childhood psychiatric disorders. That is, high ADHD traits are mainly attributable to genes (nature). How does this fare for children with extremely low ADHD traits? We were surprised to find that low ADHD traits were not significantly heritable. Instead, low ADHD traits were strongly influenced by the environment (nurture). For example, the shared environment between family members influences siblings in the family to have similar low ADHD traits.
Importantly, just because high ADHD traits are heritable this doesn’t mean that environmental interventions are not effective for ADHD. Both medication and behavioural interventions such as parent management training are evidence-based treatment options for ADHD. In this light, our results are very interesting. If we can identify positive or protective environments influencing low ADHD traits, this could possibly provide clues for interventions for those with high ADHD traits or to prevent individuals from developing ADHD.
This blog is written by Corina Greven. Corina works as a post doctoral researcher on the NeuroIMAGE-project. Her research focuses on the genetic and neurobiological causes of ADHD.
Edited by Lieneke.