E-Risk is a nationally representative twin cohort study that aims to build a knowledge about how environmental and genetic factors contribute to behaviours and the development of mental health problems from childhood through to young adulthood. Through the years, data have been collected about many different topics, including mental health, obesity, asthma, school performance, criminal offending, violence victimisation, neighbourhood conditions, the family environment, and also biomarkers to investigate inflammation, gene expression, epigenetic DNA methylation, telomeres, and neuropsychological functions.