Genetic epidemiology of alcohol-induced blackouts.
BACKGROUND
Alcohol-induced blackouts (ie, periods of anterograde amnesia) have received limited recent research attention.


OBJECTIVE
To examine the genetic epidemiology of lifetime blackouts and having had 3 or more blackouts in a year, including analyses controlling for the frequency of intoxication.


METHODS
Members of the young adult Australian Twin Register, a volunteer twin panel born between January 1, 1964, and December 31, 1971, were initially registered with the panel as children by their parents between 1980 and 1982. They underwent structured psychiatric telephone interviews from February 1996 through September 2000. The current sample contains 2324 monozygotic and dizygotic twin pairs (mean [SD] age 29.9 [2.5] years) for whom both twins' responses were coded for blackout questions and for frequency of intoxication.


METHODS
Outcome Measure Data on lifetime blackouts and having had 3 or more blackouts in a year were collected within an examination of the genetic epidemiology of alcoholism.


RESULTS
A lifetime history of blackouts was reported by 39.3% of women and 52.4% of men; 11.4% of women and 20.9% of men reported having had 3 or more blackouts in a year. The heritability of lifetime blackouts was 52.5% and that of having had 3 or more blackouts in a year was 57.8%. Models that controlled for frequency of intoxication found evidence of substantial genetic contribution unique to risk for the blackouts and a significant component of genetic risk shared with frequency of intoxication.


CONCLUSIONS
The finding of a substantial genetic contribution to liability for alcohol-induced blackouts including a component of genetic loading shared with frequency of intoxication may offer important additional avenues to investigate susceptibility to alcohol-related problems.
Nelson
Elliot C
EC
Department of Psychiatry, Washington University School of Medicine and St Louis University School of Public Health, St Louis, O 63108, USA. nelsone@psychiatry.wustl.edu
Heath
Andrew C
AC
Bucholz
Kathleen K
KK
Madden
Pamela A F
PA
Fu
Qiang
Q
Knopik
Valerie
V
Lynskey
Michael T
MT
Lynskey
Michael T
MT
Whitfield
John B
JB
Statham
Dixie J
DJ
Martin
Nicholas G
NG
D000328:Adult; D000435:Alcoholic Intoxication / Q000150:complications* / Q000235:genetics*; D000437:Alcoholism / Q000150:complications / Q000235:genetics; D020324:Amnesia, Anterograde / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors