Alcohol-induced blackouts (ie, periods of anterograde amnesia) have
received limited recent research attention.
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.
Design, Setting, and Participants
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.
Main 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.
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.
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.