| dc.description.abstract | Evidence from largely independent lines of research suggests that genetic variation, environmental factors, and individual differences in cognitive biases are associated with risk for depression and anxiety. These independent lines of research, if combined, may advance our understanding of individual differences associated with such disorders. Therefore, examining genes, environments, gene-by-environment interactions, and cognitive biases associated with such affective disorders may provide further insight into their development. This thesis aimed to test this integrated theory, recently formulated in the CogBIAS hypothesis (Fox & Beevers, 2016), across three studies featuring two samples. The first sample included 74 adults, and the second sample 504 adolescents from the CogBIAS Longitudinal Study. In study one, primary data was used to assess the effects of cognitive biases on levels of affect in response to daily life events. In study two, the effects of both genes and the environment on the development of cognitive biases were assessed. In study three, the mediation of polygenic risk for major depression by cognitive biases on later anxiety and depression symptoms was explored. According to results, negative interpretation bias was significantly associated with negative perceptions of daily life events, and significantly moderated the effects of positive environmental contexts. Positive and negative life events and most candidate variants tested were associated with the development of memory and interpretation bias, with candidate variants also collectively and individually moderating the effect of life events. Finally, memory and interpretation bias were found to share genetic architecture with depression and mediate polygenic risk for major depression on later depression symptoms. Notwithstanding some statistical and methodological limitations, the current thesis provides support for elements of the CogBIAS hypothesis, whilst also suggesting that levels of positive cognitive biases may be of great importance to the development of affective disorders, and a potential target for future treatment and prevention. | en_US |
