 One study, in particular, resulted in subjects being stratified easily into two groups, those who consumed alcohol very quickly, and blacked out, and those who did not black out by drinking alcohol slowly, despite being extremely intoxicated by the end of the study.In another study hospital file data showed, that of 67 participants who abused alcohol, 39 had reported a blackout.The presence or absence of blackouts was cross-tabulated against various measures of alcohol problem severity.