Sex and Age-at-Injury as Determinants of Social Behavior Outcomes After TBI.

While our understanding of long-term disability after traumatic brain injury (TBI) has habitually focused on cognitive and sensorimotor functioning, it is increasingly appreciated that changes in social function for survivors of a brain injury are common and have a profound impact on one's quality of life. In this chapter, we highlight the consequences of TBI on social behavior, taking into account evidence from studies of patient populations as well as from preclinical animal models. After first considering the protracted nature of the development of social behavior across the lifespan, including the neurobiological networks that underlie social functioning, we discuss how TBI results in social behavior impairments and how these manifest. We focus particularly on how age-at-injury influences TBI-induced social impairments, with most of the evidence suggesting age-dependent vulnerability after injury at a younger age. In addition, we explore how biological sex is a key determinant of social behavior impairments after TBI, while gender in humans may also influence the nature and extent of social outcomes. Finally, we identify key knowledge gaps and emphasize the need for further research in the field.