Background
Fear conditioning is a traditional model for the acquisition of phobias, whereas behavioral
therapies use processes underlying extinction to treat phobic and other anxiety disorders.
Furthermore, fear conditioning has been proposed as an endophenotype for genetic studies
of anxiety disorders. Although prior studies have demonstrated that fear conditioning
and self-report fears are heritable, no studies have determined whether they share
a common genetic basis.
Methods
We obtained fear conditioning data from 173 twin pairs from the Swedish Twin Registry
who also provided self-report ratings of 16 common fears. With multivariate structural
equation modeling, we analyzed factor-derived scores for the subjective fear ratings
together with the electrophysiologic skin conductance responses during habituation,
acquisition, and extinction to determine the extent of their genetic covariation.
Results
Phenotypic correlations between experimental and self-report fear measures were modest
and, counter-intuitively, negative (i.e., subjects who reported themselves as more
fearful had smaller electrophysiologic responses). Best-fit models estimated a significant
(negative) genetic correlation between them, although genetic factors underlying fear
conditioning accounted for only 9% of individual differences in self-report fears.
Conclusions
Experimentally derived fear conditioning measures share only a small portion of the
genetic factors underlying individual differences in subjective fears, cautioning
against relying too heavily on the former as an endophenotype for genetic studies
of phobic disorders.
Key Words
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Article info
Publication history
Published online: August 16, 2007
Accepted:
June 9,
2007
Received in revised form:
June 5,
2007
Received:
August 11,
2006
Identification
Copyright
© 2008 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
