title: The association between hippocampal volume and life events in healthy twins.
abstract: Hippocampal volume deficits have been linked to life stress. However, the degree to which genes and environment influence the association between hippocampal volume and life events is largely unknown. In total, 123 healthy twins from monozygotic and dizygotic twin pairs underwent magnetic resonance imaging (MRI), and 57 healthy twins were interviewed with the Life Events and Difficulties Schedule (LEDS), with an overlap of 54 twins undergoing both MRI and the life events interview. Hippocampal volumes were segmented with Freesurfer software. Data were analyzed with OpenMx software. Smaller hippocampal volume was associated with higher severe life event load (rph = -0.39), where shared environmental factors influencing both measures fully explained the association. Hippocampal volume was not associated with total or mild life event load. Hippocampal volume showed high heritability (range, h(2) : 57%-81%) whereas life event measures were influenced by shared (c(2) ) and unique (e(2) ) environmental factors only (range, c(2) :40%-64%, e(2) : 36%-60%). The results suggested that shared environmental factors influenced the relationship between smaller hippocampal volume and severe (but not mild) stress. This indicated that particularly severe life events that were shared between twins were associated with smaller hippocampal volume. Furthermore, it is suggested to distinguish between mild and severe life events in life event research. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Florian
authors.initials: F
authors.lastname: Bootsman
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Sanne M
authors.initials: SM
authors.lastname: Kemner
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Manon H J
authors.initials: MH
authors.lastname: Hillegers
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Brouwer
authors.affiliation: Reinier Van Arkel's, Hertogenbosch, The Netherlands.
authors.forename: Ronald
authors.initials: R
authors.lastname: Vonk
authors.affiliation: Alzheimer Nederland, Amersfoort, The Netherlands.
authors.forename: Astrid C
authors.initials: AC
authors.lastname: van der Schot
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Hilleke E
authors.initials: HE
authors.lastname: Hulshoff Pol
authors.affiliation: Department of Psychiatry, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Willem A
authors.initials: WA
authors.lastname: Nolen
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: René S
authors.initials: RS
authors.lastname: Kahn
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Neeltje E M
authors.initials: NE
authors.lastname: van Haren
mesh_terms: D000328:Adult; D005260:Female; D059647:Gene-Environment Interaction; D006624:Hippocampus / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008957:Models, Genetic; D009929:Organ Size; D012984:Software; D013315:Stress, Psychological / Q000000981:diagnostic imaging*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
keywords: heritability; hippocampus; life stress; shared environment; twin study