***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : In a previous prospect i ve study , the risk of concussion and all injury was more than threefold higher among Pee Wee ice hockey players ( ages 11–12 years ) in a league that allows  bodychecking than among those in a league that does not . We examined whether two years of bodychecking experience in Pee Wee influenced the risk of concussion and other injury among players in a Bantam league ( ages 13–14 ) compared with Bantam players introduced to bodychecking for the first time at age 13 . Methods : We conducted a prospect i ve cohort study involving hockey players aged 13–14 years in the top 30 % of divisions of play in their leagues . Sixty-eight teams from the province of Alberta ( n = 995 ) , whose players had two years of bodychecking experience in Pee Wee , and 62 teams from the province of Quebec ( n = 976 ) , whose players had no bodychecking experience in Pee Wee , participated . We estimated incidence rate ratios ( IRRs ) for injury and for concussion . Results : There were 272 injuries ( 51 concussions ) among the Bantam hockey players who had bodychecking experience in Pee Wee and 244 injuries ( 49 concussions ) among those without such experience . The adjusted IRRs for game-related injuries and concussion overall between players with bodychecking experience in Pee Wee and those without it were as follows : injury overall 0.85 ( 95 % confidence interval [ CI ] 0.63 to 1.16 ) ; concussion overall 0.84 ( 95 % CI 0.48 to 1.48 ) ; and injury result ing in more than seven days of time loss ( i.e. , time between injury and return to play ) 0.67 ( 95 % CI 0.46 to 0.99 ) . The unadjusted IRR for concussion result ing in more than 10 days of time loss was 0.60 ( 95 % CI 0.26 to 1.41 ) . Interpretation : The risk of injury result ing in more than seven days of time loss from play was reduced by 33 % among Bantam hockey players in a league where bodychecking was allowed two years earlier in Pee Wee compared with Bantam players introduced to bodychecking for the first time at age 13 . In light of the increased risk of concussion and other injury among Pee Wee players in a league where bodychecking is permitted , policy regarding the age at which hockey players are introduced to bodychecking requires further consideration Introduction Persistent postconcussive symptoms ( PCSs ) is the persistence of somatic , cognitive , physical , psychological and /or behavioural changes lasting more than 1 month following concussion . Persistent concussion impacts the quality of life through impaired cognition , memory and attention affecting school performance , mood and social engagement . No large epidemiological studies have determined the true prevalence of persistent concussion symptoms . Vali date d , easy-to-use prognosticators do not exist for clinicians to identify children at highest risk . The goal of Predicting and Preventing Postconcussive Problems in Pediatrics study is to derive a clinical prediction rule for the development of persistent postconcussion symptoms in children and adolescents presenting to emergency department following acute head injury . Methods and analysis This study is a prospect i ve , multicentre cohort study across nine academic Canadian paediatric emergency departments . We will recruit the largest prospect i ve epidemiological cohort of children with concussion . Eligible children will be followed using  Post-Concussion Symptom Inventory , a vali date d tool in children as young as 5 years . Patients will follow-up at 1 , 2 , 4 , 8 and 12 weeks postinjury . The main outcome will be the presence/absence of PCSs defined as three or more persistent concussion symptoms 1 month following the injury .  1792 patients provide adequate power to derive a clinical decision rule using multivariate analyses to find predictor variables sensitive for detecting cases of persistent postconcussion symptoms . Ethics and dissemination Results of this large prospect i ve study will enable clinicians to identify children at highest risk , optimise treatment and provide families with realistic and appropriate anticipatory guidance . Ethics has been obtained through the Children 's Hospital of Eastern Ontario Research Ethics Board . Results will be disseminated at international conferences and in four manuscripts to peer- review ed journals . Trial registration This study is registered at Clinical trials.gov through the US National Institute of Health/National Library of Medicine ( NCT01873287 ; http:// clinical trials.gov/ct2/show/NCT01873287 ) BACKGROUND The etiology of schizophrenia is believed to include genetic and nongenetic factors , with the pathogenesis involving abnormal neurodevelopment . We investigated whether mild head injury during brain maturation plays a role in the expression of schizophrenia in multiply affected families . METHODS We compared the history and severity of head injuries in childhood ( age , < or = 10 years ) and through adolescence ( age , < or = 17 years ) in 67 subjects with narrowly defined schizophrenia and 102 of their unaffected siblings from 23 multiply affected families . In subjects with schizophrenia , only head injuries preceding the onset of psychosis were considered . RESULTS Subjects in the schizophrenia group ( n = 16 [ 23.9 % ] ) were more likely than the unaffected siblings group ( n = 12 [ 11.8 % ] ) to have a history of childhood head injury ( P = .04 ; odds ratio , 2.35 [ 95 % confidence interval , 1.03 - 5.36 ] ) . Subjects in the schizophrenia group with a history of childhood head injury had a significantly younger median age at onset of psychosis ( 20 years ) compared with those with no such history ( 25 years ; z = -2.98 ; P = .003 ) . The severity of head injury ranged from minimal to mild , including concussions , but within this narrow range , severity was correlated with younger age at onset ( r(s ) = -0.66 ; P = .005 ) . Head injury occurred a median of 12 years before the onset of psychosis . Results were similar if head injuries during adolescence were included , but did not achieve statistical significance . CONCLUSIONS Mild childhood head injury may play a role in the expression of schizophrenia in families with a strong genetic predisposition . Prospect i ve studies of mild head injury should consider genetic predisposition for possible long-term neurobehavioral sequelae Objectives : The question of whether any adverse cognitive or psychosocial outcomes occur after mild head injury in early childhood has evoked considerable controversy . This study examined mild head injury before age 10 and potential differences in late childhood/early adolescence as a function of severity of mild injury and age at injury . Methods : A fully prospect i ve longitudinal design tracked a large birth cohort of children . Confirmed cases of mild head injury before age 10 were divided on the basis of outpatient medical attention ( n=64–84 )  or inpatient observation  ( hospital overnight ; n=26–28 ) and compared with the non-injured remainder of the cohort ( reference group ; n=613–807 ) . A range of pre-injury and post-injury child and family characteristics were used to control for any potential confounds . Outcome after injury before and after age 5 was also assessed . Results : After accounting for several demographic , family , and pre-injury characteristics , the inpatient but not the outpatient group displayed increased hyperactivity/inattention and conduct disorder between ages 10 to 13 , as rated by both mothers and teachers . Psychosocial deficits were more prevalent in the inpatient subgroup injured before age 5 . No clear effects were evident for various cognitive/academic measures , irrespective of severity of mild injury or age at injury . Conclusions : Most cases of mild head injury in young children do not produce any adverse effects , but long term problems in psychosocial function are possible in more severe cases , perhaps especially when this event occurs during the preschool years . The view that all mild head injuries in children are benign events requires revision and more objective measures are required to identify cases at risk A 2 1/4-year prospect i ve study of children suffering head injury is described . Three groups of children were studied : ( a ) 31 children with ' severe ' head injuries result ing in a post-traumatic amnesia ( PTA ) of at least 7 days ; ( b ) an individually matched control group of 28 children with hospital-treated orthopaedic injuries ; and ( c ) 29 children with ' mild ' head injuries result ing in a PTA exceeding 1 hour but less than 1 week . A retrospective assessment of the children 's pre-accident behaviour was obtained by parental interview and teacher question naire immediately after the accident and before the behavioural sequelae of the injury could be known . Further psychiatric assessment s were undertaken 4 months , 1 year and 2 1/4 years after the initial injury . The mild head injury group showed a raised level of behavioural disturbance before the accident but no increase thereafter . It was concluded that head injuries result ing in a PTA of less than 1 week did not appreciably increase the psychiatric risk . By contrast , there was a marked increase in psychiatric disorders following severe head injury . The high rate of new disorders in children with severe head injuries who were without disorder before the accident , together with the finding of a dose-response relationship with the severity of brain injury , indicated a causal relationship . However , the development of psychiatric disorders in children with severe head injuries was also influenced by the children 's pre-accident behaviour , their intellectual level , and their psychosocial circumstances . With the exception of social disinhibition and a slight tendency for the disorders to show greater persistence over time , the disorders attributable to head injury showed no specific features OBJECTIVE The impact of mild head injury or mild traumatic brain injury ( TBI ) in children is variable , and determinants of outcome remain poorly understood . There have been no previous attempts to evaluate the impact of interventions to improve outcome . Results of previous intervention studies in adults have been mixed . This study aim ed to evaluate the impact of providing information on outcome measured in terms of reported symptoms , cognitive performance , and psychological adjustment in children 3 months after injury . METHODS A total of 61 children with mild TBI were assessed 1 week and 3 months after injury , and 58 children with mild TBI were assessed 3 months after injury only . They were compared with 2 control groups ( N = 45 and 47 ) of children with minor injuries not involving the head . Participants completed measures of preinjury behavior and psychological adjustment , postconcussion symptoms , and tests of attention , speed of information processing , and memory .  Children with mild TBI seen at 1 week were also given an information booklet outlining symptoms associated with mild TBI and suggested coping strategies . Those seen 3 months after injury only did not receive this booklet . RESULTS Children with mild TBI reported more symptoms than controls at 1 week but demonstrated no impairment on neuropsychological measures . Initial symptoms had resolved for most children by 3 months after injury , but a small group of children who had previous head injury or a history of learning or behavioral difficulties reported ongoing problems . The group not seen at 1 week and not given the information booklet reported more symptoms overall and was more stressed 3 months after injury . CONCLUSIONS Providing an information booklet reduces anxiety and thereby lowers the incidence of ongoing problems The degree to which postinjury posttraumatic stress disorder ( PTSD ) and /or depressive symptoms in adolescents are associated with cognitive and functional impairments at 12 and 24 months after traumatic brain injury ( TBI ) is not yet known . The current study used a prospect i ve cohort design , with baseline assessment and 3- , 12- , and 24-month followup , and recruited a cohort of 228 adolescents ages 14 - 17 years who sustained either a TBI ( n = 189 ) or an isolated arm injury ( n = 39 ) . Linear mixed-effects regression was used to assess differences in depressive and PTSD symptoms between TBI and arm-injured patients and to assess the association between 3-month PTSD and depressive symptoms and cognitive and functional outcomes . Results indicated that patients who sustained a mild TBI without intracranial hemorrhage reported significantly worse PTSD ( Hedges g = 0.49 , p = .01 ; Model R(2 ) = .38 ) symptoms across time as compared to the arm injured control group . Greater levels of PTSD symptoms were associated with poorer school ( η(2 ) = .07 , p = .03 ; Model R(2 ) = .36 ) and physical ( η(2 ) = .11 , p = .01 ; Model R(2 ) = .23 ) functioning , whereas greater depressive symptoms were associated with poorer school ( η(2 ) = .06 , p = .05 ; Model R(2 ) = .39 ) functioning Background Concussion is one of the most commonly occurring injuries in sport today . The Sport Concussion Assessment Tool ( SCAT ) is a commonly used paper neurocognitive tool . To date , little is known about SCAT baseline normative values in youth athletes . Objective The purpose of this study was to determine normative values on the SCAT for male and female youth hockey players . Methods This is a secondary data analysis of pooled data from three prospect i ve cohort studies examining the risk of injury in paediatric ice hockey players aged 9–17 years . A preseason baseline demographic and injury history question naire was completed by each player . Results A total of 4193 players completed SCATs at baseline and were included in the analysis . 781 players ( 18.6 % ) reported a previous history of concussion . Fatigue and low energy followed by headache were the most commonly reported symptoms in all players . The majority of youth players could recite all five words 
    Output:
    
Based on the literature included in this systematic review , psychological and psychiatric problems in children with a history of mTBI were found to be more prevalent when mTBI is associated with hospitalization , when assessment occurs earlier in the recovery period ( that is , resolves over time ) , when there are multiple previous mTBIs , in individuals with preexisting psychiatric illness , when outcomes are based on retrospective recall , and when the comparison group is noninjured healthy children ( as opposed to children with injuries not involving the head ) .
In the absence of true reports of preinjury problems and when ideally comparing mild TBI to non-TBI injured controls , there is little evidence to suggest that psychological , behavioural , and /or psychiatric problems persist beyond the acute and subacute period following an mTBI in children and adolescents