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Fragmentary and En Bloc Blackouts: Similarity and Distinction among Episodes of Alcohol-Induced Memory Loss

Bryan Hartzler, Kim Fromme

Objective: En bloc and fragmentary blackouts are distinguishable forms of alcohol-induced amnesia. The former are instances of full and permanent memory loss for intoxicated events, whereas the latter are episodes for which retrieval of experiences is facilitated by provision of cues. Beyond this nosological difference, little is known about descriptive dimensions of the two blackout types. The current study assessed their characteristics as reported by a group of heavy drinking young adults. Method: A sample of 136 young adult volunteers (54% male; mean [SD] age = 22.71 [2.23]) were administered a Time-Line Follow-Back assessment, expanded to gather descriptive information about the occurrence and characteristics of en bloc and fragmentary blackouts. Results: Although overall reporting of blackouts by the sample mirrored rates reported in prior research, prevalence and incidence of fragmentary blackouts were more than threefold those of en bloc blackouts. A surprising finding was that the two blackout types exhibited a similar range and distribution of corresponding blood alcohol concentrations. Most en bloc blackouts involved concurrent use of illicit substances; polysubstance use was reported for few fragmentary blackouts. In addition, subjective evaluations of en bloc blackouts were quite negative, whereas fragmentary blackouts were evaluated as only mildly negative. Conclusions: Beyond nosological distinctions, en bloc and fragmentary blackouts differ on several descriptive dimensions. The collective findings expand understanding of diversity in experiences that accompany memory loss after drinking. (J. Stud. Alcohol 64: 547-550, 2003)