Participants in the mindfulness-based stress reduction group demonstrated greater improvement in self-reported PTSD symptom severity during treatment ( change in mean PTSD Checklist scores from @ to @ vs @ to @ with present-centered group therapy ; between-group difference , @ ; @ % CI , @-@ @ ; P = @ ) and at @-month follow-up ( change in mean scores from @ to @ vs @ to @ , respectively ; difference , @ ; @ % CI , @-@ @ , P < @ ) .