A traumatic brain injury (TBI) occurs when a mechanical force to the head distorts brain function. This interruption in function can result in temporary, long term or permanent brain damage or even death. Research on TBI's among children and adolescents remains limited, especially on caregiver-level factors that might modify their susceptibility to this form of trauma. This thesis augments and extends prior research findings which suggest that even less severe TBIs in childhood may increase the risk of behavioral, social and psychiatric sequalae later in life. It examines the geographic patterning and distribution of pediatric TBI and provides additional information on the possible relationship between parent health and risk for TBI involving the children under their care. The latter two papers focus on well defined populations in Finland, with some attention given to global comparison. 

Three studies are elaborated and consecutively numbered as interconnected chapters in this thesis. The first (I) Study examined previously published peer-reviewed data on pediatric TBI outcomes in the form of a systematic review. Its aim was to systematically review existing empirical evidence concerning neuropsychological, psychosocial and academic outcomes subsequent to mild and moderate TBI during childhood and adolescence. Altogether data on 8 553 participants under 18 years of age who experienced mild or moderate TBIs were included. This represented a total of 55 studies published between January 2008 and April 2013. The overall results of this systematic review indicated that not all children and adolescents who have experienced a moderate or mild TBI recover without sustaining long term problems and that significant disparity existed in the literature regarding this finding. 

The second Study (II) examined data on 21 457 Finnish children and adolescents who were hospitalized with a TBI between 1998 and 2012. The data were derived from the Finnish National Hospital Discharge Register and several forms of TBI were considered identified by their ICD-10 codes. These data were divided into five age categories which were used as the basis for calculating overall and per group incidence rates. The study found that males were overrepresented in Finnish injury statistics with concussions being the most common form of brain injury among both sexes. The study also revealed that compared with countries having similarly robust data on pediatric TBI such as Australia, USA and Fiji, that Finnish children and adolescents had higher rates of TBI. Substantial differences existed in the adjusted population injury rates by geographic region in Finland which may be attributable to diagnostic practices and the possible role of distance to emergency care centers. 

The third Study (III) utilizes data on 60 069 Finnish children and their parents derived from the 1987 Finnish Birth Cohort. It examines the role that demographic and parent mental health attributes exercise in modifying underlying susceptibility for TBI among Finnish children and adolescents. High educational attainment and high socio-economic status of parents were found to be factors which were associated with a lowered risk of TBI among Finnish children and adolescents. Among the mental health attributes among parents considered, several were associated with increased rates of TBI among children under their care. For example mood disorders, personality disorders, schizophrenia and behavioral disorders among both mothers and fathers were associated with statistically significantly increased rates of TBI among children.