Theory of mind after mild TBI in preschool children : a longitudinal perspective

Preschool children (≤ 5 years old) are at particular risk of sustaining traumatic brain injury (TBI) and 90% of these injuries are mild in nature (mTBI). A substantial amount of research has provided evidence of acute and, in more isolated cases, long-term cognitive, behavioral, and psychiatric consequences following mTBI. In the last two decades, there has been an increase in scientific attention dedicated to the social and socio-cognitive (the cognitive functions that underpin socialisation) sequelae of pediatric mTBI; however, research has almost exclusively been conducted with school-aged children and adolescents. Thus, the literature concerning the social repercussions of mTBI remains comparatively sparse in preschool children, with only two studies that have examined social competence following mTBI. No study has investigated the consequences of early (preschool) mTBI on social cognition. Therefore, the overall objective of this thesis was to expand our understanding of the impact of preschool mTBI on social cognition. More specifically, we addressed an aspect of social cognition that typically emerges during the preschool years, that of theory of mind (ToM), known as the capacity to put oneself in others’ shoes and understand their perspective.     The first article examined two subcomponents of ToM, that of false belief understanding and desires and emotions reasoning, 6 months post-mTBI. The findings indicate that preschool children (18 to 60 months) who sustain mTBI have significantly poorer ToM skills compared to typically developing peers 6 months post-injury.   The second article focused on the debate in the mTBI literature concerning the most appropriate control group for isolating outcomes that are specific to brain injury. Indeed, it is argued that the choice of the control group (community controls vs. injured counterparts) is of paramount importance because it dictates the conclusions that can be drawn in TBI research. It is argued that brain-injury-specific effects constitute a valid conclusion only when compared to injured peers because in general, children who sustain accidental injuries (whether orthopedic or to the head) share certain pre-existing cognitive characteristics (e.g., impulsivity, attentional difficulties) that not only make them more accident-prone but may also be the origin of post-mTBI difficulties. Thus, the aim of the second paper was to determine whether the poorer ToM skills detected in preschool children with mTBI are the result of a general-injury effect or a brain-injury-specific effect. A second goal of this article was to examine the evolution of ToM skills following mTBI, from 6 months to 18 months post-injury. To do so, we compared children with mTBI to both a community control group and an orthopedic injury (OI) control group. The findings indicate that children who sustain mTBI performed worse on the desires and emotions reasoning task 6 months post-injury compared to both injured and uninjured counterparts, and this discrepancy in performance was maintained 18 months post-mTBI. Lastly, the third goal of this study was to investigate the link between performances on ToM tasks and social abilities, as measures by parental questionnaires. Overall, these two studies demonstrate a persistent brain-injury-specific effect on ToM skills following early mTBI, and poorer ToM skills are associated with reduced social functioning.  This thesis provides evidence that early mTBI can interfere with socio-cognitive development, notably in terms of its repercussions on ToM. These findings support the theory according to which the young, immature brain is more vulnerable to brain insult. Importantly, our studies demonstrate that extrapolation from conclusions drawn with older pediatric age groups may be erroneous because the developmental issues faced by preschool children are fundamentally different. Indeed, neurodevelopmental immaturity may be a driving force that dictates the impact of mTBI on socio-cognitive functioning.

Keyphrases: Pediatric, Preschool children, Traumatic brain injury, Concussion, Social cognition, Social skills, Perspective taking, Theory of mind, False belief understanding, Long-term