6th Annual Scholarship (April 2005)

​             made to  Dr. Nathan Gillespie from Australia

on the subject of A genome wide scan for adolescent personality: Psychoticism, Extraversion, Neuroticism and Lie

Report Abstract (446 words):

To date, there have been numerous genome wide scans for Neuroticism, Neuroticism-like traits and genetically related measures of mood and anxiety. Despite the interest in Neuroticism, there are no known genome wide scans for adult Extraversion or Psychoticism. Much less is known about the genetics of adolescent personality. The aim of this paper is to report a genome-wide scan based on measures of adolescent personality from Australian twins and their siblings.

Data for this study was collected as part of ongoing studies into the development of melanocytic naevi and cognition at ages 12, 14 and 16. At each interview, twins, cotwins and their siblings were asked to complete the full 81 item Junior Eysenck Personality Questionnaire (JEPQ) which assesses the three major dimensions of personality: Psychoticism, Extraversion and Neuroticism. In addition, the questionnaire contained the Lie scale which is a measure of social desirability. Complete phenotypic data were available from 2086 twin individuals and 511 siblings.

Blood or three buccal cell samples were obtained from twins, siblings and most parents for blood grouping and DNA extraction. There were 439 families with a minimum of 1 sib-pair and which had complete genotypic and phenotypic data.

Multipoint identity by descent probabilities were calculated at each of the autosomal markers using MERLIN. For each wave of data collection, variance components linkage analyses were run in Mx and LOD scores plotted. The Mx variance components method has the advantage of being able to model the effects of age and sex on the means for each of the personality dimension.

We found only one area of significant linkage on chromosome 4 for Lie. We found no linkage for Psychoticism, Extraversion or Neuroticism. There were just two regions of suggestive linkage; Extraversion on chromosome 3 and Psychoticism on chromosome 7.

An advantage of this study was the availability of multiple measurements on the same individuals across time. Normally this would provide the powerful option of performing multivariate QTL analysis to increase the power to detect QTLs which affect measurements pleiotropically. Multivariate QTL analysis can also provide supporting evidence for linkage if a signal is present in the same region at other ages. Yet despite evidence of significant additive genetic continuity across the three waves based on genetic simplex modeling using the same data, there was little congruency between the LOD score curves at 12, 14 and 16 years.

To our knowledge, this study is the first to show a genome wide scan of adolescent personality measures, and certainly the first genome wide scan for the dimensions of Psychoticism, Extraversion and Lie. We are currently working on incorporating mood and affective measures while increasing the sample size to increase power to detect linkage.

Scholarship 6