Beyond the first years of life, the risk of dying increases with age, but more or less quickly. Early adulthood is marked by a temporary increase of this risk, in particular for young males. The origins of this excess mortality remain poorly understood and are hotly debated. Does it concern all young people? Is it attributable to biological or to social factors? Adrien Remund describes the excess mortality of a cohort of young adults living in Switzerland and focuses on the moderating or amplifying role of socioeconomic factors.