Children and their families who attended an emergency department following a single traumatic incident and who agreed to participate in a psychological treatment study (N = 211) were compared with nonparticipants (N = 2333) on several measures of trauma and injury severity: duration of admission and heart rate in the emergency department, emergency transport and admission to hospital, injury severity score, and triage code. Within the nonparticipant population, those who requested further information about the study (N = 573) were exposed to more severe trauma or injury than other nonparticipants (N = 1760). In addition, participants were exposed to more severe trauma or injury than either group of nonparticipants. These observations indicate that those exposed to more severe trauma or injury do not avoid participation in psychological treatment studies. Findings can therefore be generalized to those with more severe exposure, but not to the population as a whole
