Nonresponse to a population-based postdisaster postal questionnaire study.

We examined nonparticipation in a 2-year postdisaster mail survey of Norwegian tourists evacuated from countries affected by the 2004 tsunami. One hundred seventy-one persons out of a random sample of 330 nonparticipants were telephone interviewed concerning disaster exposure, current posttraumatic stress reactions, and reasons for not participating. Fewer nonparticipants than participants had been in a place directly affected by the tsunami. Nonparticipants reported less perceived threat of death and lower levels of posttraumatic stress reactions. Reasons for not participating were "lack of interest or time" (39.2%), "lack of relevant experiences" (32.2%), and "too personal or emotionally disturbing" (15.2%). Our findings suggest that postdisaster studies may be biased in the direction of more severe disaster exposure and pronounced posttraumatic stress reactions.