[evol-psych] Fears and phobias: reliability and heritability
- Psychological Medicine (1999), 29:539-553. Cambridge University Press.
Copyright © 1999 Cambridge University Press
Fears and phobias: reliability and heritability
K. S. KENDLER a1 c1, L. M. KARKOWSKI a1 and C. A. PRESCOTT a1
a1Virginia Institute for Psychiatric and Behavioral Genetics and the
Departments of Psychiatry and Human Genetics, Medical College of Virginia of
Virginia Commonwealth University, VA, USA
Background. Familial factors, which are partly genetic, influence risk for
phobias. Prior family and twin studies, however, were based on a single
lifetime assessment, which may be only moderately reliable.
Methods. We obtained, 8 years apart, two assessments of lifetime history of
five unreasonable fears and phobias (agoraphobia and social, situational,
animal and blood-injury phobia) from face-to-face and telephone interviews from
1708 individual female twins from a population-based registry. We also
obtained, 1 month apart, test-retest reliability on 192 twins. We fitted, using
the program Mx, a measurement model that estimates the role of genetic and
environmental risk factors correcting for measurement error.
Results. Short-term reliability of the five phobias was modest (mean
[kappa]=0·46), but higher than long-term stability (mean [kappa]=0·30).
Unreliability occurred both for subject recall of unreasonable fears and for
interviewer assessment of which fears constituted phobias. Examining fears and
phobias together, in a multiple threshold model, results suggested that twin
resemblance was due solely to genetic factors, with estimated total
heritabilities, corrected for unreliability, of: any 43%, agoraphobia 67%,
animal 47%, blood/injury 59%, situational 46% and social 51%. With the
exception of animal phobia, similar results were obtained analysing phobias
Conclusions. Lifetime histories of unreasonable fears and phobias assessed at
personal interview have substantial unreliability. Correcting for
unreliability, the liability to fears and their associated phobias is
moderately heritable. Individual-specific environmental experiences play an
important role in the development of phobias, while familial-environmental
factors appear to be of little aetiological significance.
c1Address for correspondence: Professor K. S. Kendler, Virginia Institute for
Psychiatric and Behavioral Genetics, PO Box 980126, Richmond, VA 23298-0126,