Despite longstanding interest in gene-by-environment (GxE) interactions, the contribution of GxE interactions to complex disease in humans remains poorly characterised. Studies of GxE interaction are statistically challenging due to the inherent high dimensionality of environmental exposures, the increased sample size required to robustly detect GxE effects and the historic lack of large datasets that combine genetic and environmental data. In this thesis I introduce a new approach for GxE...