Factors that contribute to an inability to remember an important aspect of a traumatic event.

Dissociative amnesia is controversial. We tested other factors that could contribute to an inability to remember an important aspect of a traumatic event: how traumatic the event was, organic amnesia, dissociative state, childhood amnesia, expression suppression, sleep disturbance, repeated experiences, and ordinary forgetting. Trauma survivors who reported an inability to remember an important aspect of a traumatic event rated the event as traumatic as trauma survivors who reported no such inability to remember. Moreover, all cases of an inability to remember an important aspect of the traumatic event could be explained by at least one factor other than dissociative amnesia. These findings are contrary to dissociative amnesia. Compared to participants who reported no inability to remember an important aspect of the traumatic event, participants who did report an inability to remember were more likely to (1) have felt disconnected from their body during the traumatic event, which may have altered memory encoding, (2) have experienced sleep problems in the year after the traumatic event, which may have reduced memory consolidation, and (3) have experienced the traumatic event repeatedly, which may have led to less detailed memories. These findings have implications for the inclusion of dissociative amnesia in the DSM.