Genetic influences on quality of life throughout the life span: Genetic and environmental influences on the variation in and covariation among traits related to quality of life throughout life time and in the aged.

Miriam Mosing (2011). Genetic influences on quality of life throughout the life span: Genetic and environmental influences on the variation in and covariation among traits related to quality of life throughout life time and in the aged. PhD Thesis, School of Psychology, The University of Queensland.

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Author Miriam Mosing
Thesis Title Genetic influences on quality of life throughout the life span: Genetic and environmental influences on the variation in and covariation among traits related to quality of life throughout life time and in the aged.
School, Centre or Institute School of Psychology
Institution The University of Queensland
Publication date 2011-06
Thesis type PhD Thesis
Supervisor Dr Margaret J. Wright
Prof Nick Martin
Dr Sarah Medland
Total pages 274
Total black and white pages 274
Language eng
Subjects 17 Psychology and Cognitive Sciences
Abstract/Summary Quality of Life (QoL) throughout lifetime is characterised by good mental and somatic functioning. The burden of mental and somatic disorders has a large economic impact on society which, in addition to the predicted increase in the ageing population over the next decades, merits research towards wellbeing throughout life and especially in the aged. In recent years it has been shown that QoL measures can be superior to more objective clinical assessments for predicting disease and mortality risk, leading to the incorporation of an individual’s subjective experience of QoL into medical research and the development of validated self-reported QoL measures. Lately, the idea of predicting future QoL (in terms of mental and somatic health) based on an individual’s personality traits has received great attention and with it the hope of developing intervention strategies, decreasing negative affect leading to a better health outcome. Although both, personality and QoL, have been shown to be partly heritable, there is little research on the genetic architecture underlying the personality-QoL link. Where does the truth about QoL throughout lifetime and its relationship to personality lie – mostly in the genes or in the environment? The present thesis aimed to explore genetic and environmental influences on factors contributing to QoL and well-being throughout lifetime and in the elderly using the twin design. Before presenting the six main studies, a literature review is presented, covering relevant theory and research on the key areas of importance to this thesis, including project aims and significance. Subsequently, based on two publications on the methodology of behaviour genetics, practical aspects of implementing the research as well as measures and analytic techniques are covered. The first paper explored the genetic architecture of the relationship between optimism, mental and self-rated health, revealing moderate heritability of all three traits ranging between 34% (mental health) and 46% (self-rated health) and that most of the covariance between the traits was due to shared genetic influences. In addition, we found some strong, though not significant, indication of sex differences in the genetic aetiology in and between the three traits. The second paper was an attempt to replicate the findings of the previous study, increasing the sample size and power by including a sample of Swedish twins to explore potential sex differences in the aetiology of these traits. However, results showed that, although we found the same pattern in the Swedish sample, a strong indication for more genetic influences on variation in and covariation between the traits in females than in males, the sex differences were still non-significant. Given the relatively high correlation of neuroticism with optimism and mental health, in the next study we explored genetic and environmental influences on the relationship between neuroticism, optimism and mental health. The modelling results showed that despite neuroticism being correlated with both optimism and mental health, optimism remains a significant predictor of mental health after controlling for the mediating effects of neuroticism. However, the genetic covariation between optimism and mental health could entirely be explained by a set of genes shared with neuroticism, indicating that the predictive value of optimism for mental health is solely due to non-shared environmental influences once neuroticism is controlled for. The fourth paper investigated the relationship between personality and mortality revealing a significant relationship between optimism, extraversion, psychoticism and longevity while neuroticism and social desirability showed no relationship with all-cause mortality. We also explored the personality-mortality link on the genetic level, finding some indication for genetic influences on these associations. The fifth study aimed to find specific genes underlying QoL. As Self-rated health not only showed the highest heritability estimate of the QoL-related traits explored here, but also has been shown to be a good indicator of QoL, we established a consortium aiming for a large Genome-Wide Association Study (GWAS) Meta-Analysis on self-rated health. The study presented here was a preliminary GWAS on more than 7000 Australian twins. Results showed that no SNPs reached genome-wide significance, indicating that self-rated health may be influenced by a large number of SNPs with small effect size. Hope remains that the meta-analysis including data from more than 12 countries will have enough power to identify at least some of these SNPs. The sixth and last study solely focused on the interrelation between traits/disorders falling under the mental health domain of QoL. By exploring the genetic aetiology of the comorbidity between three anxiety disorders and Major Depression we could show large genetic overlap between these disorders, emphasizing the importance of thorough exploration of the environmental as well as genetic aetiology of mental disorders before categorization in disease manuals. Finally, a synthesis of the key findings of each study is presented including a discussion of potential limitations of the research. This section also provides a critical assessment of the implications of the present findings as well as future research in this field.
Keyword Quality of Life, well-being, healthy ageing, personality, self-rated health, mental health, twin modeling, optimism, mortality, life-span
Additional Notes landscape pages: 29, 33, 34, 138, 237, 260

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Created: Tue, 29 Nov 2011, 16:02:54 EST by Mrs Miriam Mosing on behalf of Library - Information Access Service