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A Twin Study of Lifetime Generalized Anxiety Disorder (GAD) in Older Adults: Genetic and Environmental Influences Shared by Neuroticism and GAD

Published online by Cambridge University Press:  21 February 2012

Margaret-Anne Mackintosh ,
Margaret Gatz ,
Julie Loebach Wetherell  and
Nancy L. Pedersen
Margaret-Anne Mackintosh*
Affiliation:
Department of Psychology, University of Southern California, Los Angeles, California, United States of America. [email protected]
Margaret Gatz
Affiliation:
Department of Psychology, University of Southern California, Los Angeles, California, United States of America; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Julie Loebach Wetherell
Affiliation:
Department of Psychiatry, University of California, San Diego and VA San Diego Healthcare System, San Diego, California, United States of America.
Nancy L. Pedersen
Affiliation:
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Psychology, University of Southern California, Los Angeles, California, United States of America.
*
*Address for correspondence: Margaret-Anne Mackintosh, Seeley G. Mudd Building, Room 524, Department of Psychology, 3620 McClintock Ave, University of Southern California, Los Angeles, CA 90089-1061, USA.

Abstract

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The nature of Generalized Anxiety Disorder (GAD) and worry across the lifespan remains incompletely understood. We investigated genetic and environmental influences on GAD and the proportion of genetic and environmental variation in GAD that is shared with neuroticism in older adult twins. Participants included 1618 monozygotic and 2291 same-sexed dizygotic twin pairs from the Swedish Twin Registry aged 55 to 74. Participants provided personality information in 1973 and also participated in a telephone screening between 1998 and 2002 that included an assessment for lifetime GAD. Univariate biometric models indicated that both GAD and neuroticism were moderately heritable (.27 and .47, respectively), while the balance of variation reflected environmental factors unique to the individual. Bivariate analyses indicated that approximately one third of the genetic influences on GAD were in common with genetic influences on neuroticism, while individual specific environmental influences were virtually unshared between GAD and neuroticism. Analyses of sex effects suggested that men and women differed in the frequency of lifetime GAD and level of neuroticism; however, no sex differences for genetic and environmental influences for either trait were identified.

Type
Articles
Information
Twin Research and Human Genetics , Volume 9 , Issue 1 , 01 February 2006 , pp. 30 - 37
Copyright
Copyright © Cambridge University Press 2006