Background: Although genetic and environmental risk factors for schizophrenia (SCZ) and major depressive disorder (MDD) are well established, it is not clear whether the exposure to these environmental risks is genetically confounded through a mechanism known as gene- environment correlation (rGE). Identifying whether rGE is implicated in the aetiology of these two psychiatric disorders may help our understanding of how to treat or prevent psychopathologies. Objective: This thesis aimed to investigate whether known environmental risk factors are correlated with the genetic susceptibilities to SCZ/MDD across three British community cohorts in childhood, adulthood and across the different developmental periods over time. We also wished to compare findings from a systematic literature review of empirical rGE studies for SCZ and depression to our own results. Methods: Polygenic risk scores (PRS), which were derived from existing genome-wide associations studies (GWAS), were utilised to investigate the correlation between known environmental risk factors and the genetic liability to SCZ/MDD. For the systematic literature review we searched seven databases for publications reporting rGE for either psychopathology in participants of any age. Results: We found associations between the genetic risk for SCZ and several psychosocial risk factors, such as marital status, whilst the genetic susceptibility to MDD was more strongly correlated with indicators of adverse socio-economic status across childhood and adulthood. Overall, the majority of rGE correlations remained stable across the investigated developmental periods. In contrast to our own results, rGE associations for SCZ and depression which were identified in the systematic literature review were largely the same across the included articles. Conclusion: In summary, our findings propose that several known psychosocial and environmental risk factors for either SCZ or MDD are at least partially correlated with the genetic liability for these psychopathologies in childhood as well as adulthood
