title: No cumulative effects for one or two previous concussions.
abstract: BACKGROUND
  Sports medicine clinicians and the general public are interested in the possible cumulative effects of concussion.
  
  
  OBJECTIVE
  To examine whether athletes with a history of one or two previous concussions differed in their preseason neuropsychological test performances or symptom reporting.
  
  
  METHODS
  Participants were 867 male high school and university amateur athletes who completed preseason testing with ImPACT version 2.0. They were sorted into three groups on the basis of number of previous concussions. There were 664 athletes with no previous concussions, 149 with one previous concussion, and 54 with two previous concussions. Multivariate analysis of variance was conducted using the verbal memory, visual memory, reaction time, processing speed, and postconcussion symptom composite scores as dependent variables and group membership as the independent variable.
  
  
  RESULTS
  There was no significant multivariate effect, nor were there any significant main effects for individual scores. There was no measurable effect of one or two previous concussions on athletes' preseason neuropsychological test performance or symptom reporting.
  
  
  CONCLUSIONS
  If there is a cumulative effect of one or two previous concussions, it is very small and undetectable using this methodology.
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada. giverson@interchange.ubc.ca
authors.forename: G L
authors.initials: GL
authors.lastname: Iverson
authors.forename: B L
authors.initials: BL
authors.lastname: Brooks
authors.forename: M R
authors.initials: MR
authors.lastname: Lovell
authors.forename: M W
authors.initials: MW
authors.lastname: Collins
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001265:Athletic Injuries / Q000503:physiopathology*; D001924:Brain Concussion / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology; D013177:Sports