IL6 and depressive symptom measurement: A possibility is that the identified genetic effects emerge in late adolescence, which is in line with the antagonistic pleiotropy hypothesis generated by Cole et al. (2011) for the effects of IL6. Previous longitudinal work with twins has also found changes in genetic and environmental influences on depression (Lau & Eley, 2006; Kendler, Gardner, & Lichtenstein, 2008).