Through genome wide association studies (GWAS), common genetic variants have been identified that are associated with alcohol, tobacco and caffeine use in the general population, allowing the generation of polygenic risk scores (PRS) for these substances. However, uncertainty remains as to whether these variants also predict use in pregnancy or at other time points in life.
Further investigation is required to confirm if these previously found genetic variants are predictive of alcohol, tobacco or caffeine use in specific subpopulations in ALSPAC; in adults (as a positive control), pregnancy, and adolescence. These variants may also have considerable pleiotropic effects, affecting the outcome through pathways other than the exposure of interest. As consumption of alcohol, tobacco and caffeine is highly comorbid with mental health problems, it is possible that common genetic variants are predisposing individuals for both an increased consumption of these substances, and development of mental health problems. A PheWAS tests the association of a single or set of genetic risk variants with a finite group of human traits, termed “the phenome”. The strength of the ALSPAC data is its longitudinal design, that enables to track health behaviour over a long period of time.