Concussion May Not Affect IQ in Children

Children’s intelligence quotient (IQ) scores are not significantly different in the first months after concussion compared with before concussion, data suggest.

In a multicenter study of almost 900 children with concussion or orthopedic injury, differences between groups in full-scale IQ (Cohen’s d = 0.13) and matrix reasoning scores (d = 0.16) were small.

Keith Owen Yeates, PhD

“We draw the inference that IQ scores are unchanged, in the sense that they’re not different from [those of] kids with other types of injuries that don’t involve the brain,” study author Keith Owen Yeates, PhD, Ronald and Irene Ward Chair in Pediatric Brain Injury and a professor of psychology at the University of Calgary, told Medscape Medical News.

The study was published July 17 in Pediatrics.

A Representative Sample

The investigators analyzed data from two prospective cohort studies of children who were treated for concussion or mild orthopedic injury at two hospitals in the United States and five in Canada. Participants were aged 8-17 years and were recruited within 24 hours of the index event. Patients in the US completed IQ and performance validity testing at 3-18 days after injury. Patients in Canada did so at 3 months after injury. The study used the short-form IQ test. The investigators included 866 children in their analysis.

Using linear modeling, Bayesian analysis, and multigroup factor analysis, the researchers found “very small group differences” in full-scale IQ scores between the two groups. Mean IQ was 104.95 for the concussion group and 106.08 for the orthopedic-injury group. Matrix reasoning scores were 52.28 and 53.81 for the concussion and orthopedic-injury groups, respectively.

Vocabulary scores did not differ between the two groups (53.25 for the concussion group and 53.27 for the orthopedic-injury group).

The study population is “pretty representative” from a demographic perspective, although it was predominantly White, said Yeates. “On the other hand, we did look at socioeconomic status, and that didn’t seem to alter the findings at all,” he added.

The sample size is one of the study’s strengths, said Yeates. “Having 866 kids is far larger, I think, than just about any other study out there.” Drawing from seven children’s hospitals in North America is another strength, he said. “Previous studies, in addition to having smaller samples, were from a single site and often recruited from a clinic population, not a representative group for a general population of kids with concussion.”

The findings must be interpreted precisely, however. “We don’t have actual preinjury data, so the more precise way of describing the findings is to say they’re not different from kids who are very similar to them demographically, have the same risk factors for injuries, and had a similar experience of a traumatic injury,” said Yeates. “The IQ scores for both groups are smack dab in the average range.”

Overall, the results are encouraging. “There’s been a lot of bad news in the media and in the science about concussion that worries patients, so it’s nice to be able to provide a little bit of balance,” said Yeates. “The message I give parents is that most kids recover within 2-4 weeks, and we’re much better now at predicting who’s going to [recover] and who isn’t, and that helps, too, so that we can focus our intervention on kids who are most at risk.”

Some children will have persisting symptoms, but evidence-based treatments are lacking. “I think that’ll be a really important direction for the future,” said Yeates.

Graduated Return

Commenting on the findings for Medscape Medical News, Michael Esser, MD, a pediatric neurologist at Alberta Children’s Hospital and an associate professor in pediatrics at the University of Calgary, said that they can help allay parents’ concerns about concussions. “It can also be of help for clinicians who want to have evidence to reassure families and promote a graduated return to activities,” he said. “In particular, the study would support the philosophy of a graduated return to school or work, after a brief period of rest, following concussion.” Esser did not participate in the study.

Michael Esser, MD

The research is also noteworthy because it acknowledges that the differences in the design and methodology used in prior studies may explain the apparent disagreement over how concussion may influence cognitive function.

“This is an important message,” said Esser. “Families struggle with determining the merit of a lot of information due to the myriad of social media comments about concussion and the risk for cognitive impairment. Therefore, it is important that conclusions with a significant implication are evaluated with a variety of approaches.”

The study received funding from the US National Institutes of Health and the Canadian Institutes for Health Research. Yeates disclosed relationships with the American Psychological Association, Guilford Press and Cambridge University Press. He has received grant funding from the Canadian Institutes of Health Research, the National Institutes of Health, Brain Canada Foundation, and the National Football League Scientific Advisory Board. He also has relationships with the National Institute for Child Health and Human Development, National Institute of Neurologic Disorders and Stroke, National Pediatric Rehabilitation Resource Center, Center for Pediatric Rehabilitation, and Virginia Tech University. Esser has no relevant relationships to disclose.

Pediatrics. Published July 17, 2023. Full text

Richard Mark Kirkner is a medical journalist based in the Philadelphia area.

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