Objective: The prevalence of mild traumatic brain injury (mTBI) in preschoolers (0-5 years) is high and its effects are understudied. Childhood is an important time for brain and functional development and acquiring a brain insult during this period could be detrimental. Studies conducted to date indicate that early TBI may have adverse cognitive, behavioral and social consequences. One study by our group found that preschool children with mTBI had poorer performance on theory of mind (ToM) tasks 6-months post-injury compared to children with orthopedic injuries (OI) and to typically developing children (TDC), suggesting a brain-injury-specific effect. These differences were found to persist up to 18 months post-injury and to correlate with social competence. The objectives of the current analyses were to establish if differences in ToM persist at 30 months post-injury and if reduced ToM is associated with changes in global social competence.

Methods: Children with mTBI and OI between 18 and 60 months of age were recruited at the emergency department of a tertiary care pediatric hospital and were followed-up at 6-, 18- and 30-months post-injury. 64 children (mean (M) age= 69.6, SD= 11.2 months, 26 boys) with mTBI participated in the 30-month follow-up and their performance was compared to 38 children with OI (M age=65.4, SD=11.7 months, 15 boys) and 56 children (M age=68.3, SD=11.7 months, 29 boys) recruited from the community (TDC). At 30 months post-injury they completed a battery of cognitive and social tasks including measures of ToM: False Belief Stories and Content to Self and to Others. Their parents completed the Social subscale of the Adaptive Behavior Assessment System (ABAS Social) as an indicator of social competence. 

Results: The mTBI group did not significantly differ from the OI or TDC groups on any of the ToM tasks: False Belief Stories: F(2,146)= 1,05, p= .35, Content to Self: F(2,140)= 2,12, p=.13; Content to Others: F(2,138)= 0,92, p= .40. Hierarchical regression analysis indicated that sex, SES and age significantly contributed to global social competence at 30 months post-injury (F(1,55) =9.94, p=.0001), but the inclusion of ToM abilities did not explain any additional variance in social competence at 30 months post-injury (F change (1,54)= .11, p=.74). 

Conclusion: The findings indicate that post-mTBI differences in ToM that were present at 6- and 18-months post-injury resolved at 30 months post-injury. The data suggest that it may take up to 30 months for young children who sustain mTBI to return to typical age-related levels of social cognition, as measured by ToM. Encouragingly, reduced social cognition (ToM) observed in the first year and a half post-injury does not seem to affect social competence in the very long term.

The effects of early, mild traumatic brain injury on theory of mind 30 months post-injury