There have been many intergenerational animal studies, as well as a few human studies looking at maternal exposure as a modifier of offspring BDNF methylation, for example, studies of trauma and fear (Pilkay et al., 2020), bi‐polar disorder (Duffy et al., 2019), and depressive symptoms (Braithwaite et al., 2015). The gene discussed is BDNF; the disease is bipolar disorder.