A few weeks ago I reviewed a study on the long-term effects of Mild Traumatic Brain Injury (TBI) in children. I mentioned in that review that previous research led to the likely incorrect assumption that the effects of mild TBI were temporary and that most kids would recover without noticeable effects within a few months. Unfortunately that study showed that children with mild TBI continue to show sub-clinical emotional and behavioral symptoms as late as 12-months after the injury.
This past weekend I came across a new study that expand upon those findings. Researchers in New Zealand were able to examine data from a large cohort of children that were born in 1977 and who had participated in a comprehensive epidemiological examination of various aspects of child development. The authors of this particular study were interested in examining three specific issues. First, most previous studies on the effects of TBI have used children of several ages, so it is not clear if TBI leads to more severe long-term effects when the injury occurs during specific ages, such as early childhood (a critical time for brain development). Second, most previous studies of TBI have followed patients for a long as 12-months, which limits our understanding of the effects of brain injuries years after the accidents. Finally, longitudinal investigations of TBI have also focused on more severe injuries, thus we know more about the long term effects of severe brain injuries than about the effects of mild (yet much more common) injuries.
You can find more information about TBI in children from the US Department of Health and Human Services.
The study included 932 children born in 1977. The history of TBI during early childhood (before age 5) was obtained via interviews and a review of their medical history. The authors identified 81 cases and divided them into an inpatient and an outpatient group, based on whether the child had to be hospitalized overnight after the injury. This distinction resulted in 60 outpatient cases, 21 inpatient cases, and 851 non-injury cases. These children were then assessed for the presence of ADHD and conduct disorder symptoms between the ages of 7 and 13.
1. As you can see in the figure below, children who experienced a mild TBI that required hospitalization (inpatient TBI) had significantly higher ADHD symptoms than TBI patients who were not hospitalized and non-injured children. Surprisingly, there were no differences between the mild TBI cases that didn’t require hospitalization and those who were never injured.
2. The figure below shows the rate of conduct disorder symptoms between the ages of 7 to 13. The results were generally similar to those obtained for ADHD symptoms. Children who experienced a TBI that required hospitalization had significantly higher conduct disorder symptoms than the other two groups. Most importantly, or maybe even alarming, the difference between these groups appeared to increase with age. That is, while the non-injured group as well as the outpatient TBI cases did not change in conduct disorder symptoms across the ages 7 to 13, the impatient TBI group show an increase of symptoms across these ages.
The results of this study provide support for the idea that mild TBI experienced during early childhood increases the risk of developing behavioral problems during middle childhood and adolescence. However, the results seem to suggest that this effect is limited to TBI cases that require overnight hospitalization.
Are there other possible interpretations? Certainly. The most clear limitation of the study is that although the authors controlled for a number of possible explanatory variables (gender of the child, birthweight, family exposure to adverse events, SES, etc), the authors could not control for the presence of ADHD or conduct disorders symptoms in early childhood. Thus there is the possibility that children with high rates of ADHD symptoms in early childhood were more likely to experience a mild TBI requiring hospitalization, and also more likely to show high levels of ADHD symptoms in middle childhood. Furthermore, it is still possible that another variable not examined in the study made some kids more likely to have TBI injuries and also more likely to have ADHD and conduct disorders symptoms. Nonetheless, the data strongly links TBI history to the presence of ADHD and conduct disorder symptoms years after the injury, and regardless of the underlying mechanism, the study suggests that parents and clinicians should pay close attention to the possible consequences of mild TBI in early childhood.
Reference: McKinlay, A., Grace, R., Horwood, L., Fergusson, D., & MacFarlane, M. (2009). Long-term behavioural outcomes of pre-school mild traumatic brain injury Child: Care, Health and Development DOI: 10.1111/j.1365-2214.2009.00947.x
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