Four of the six studies that suspected that FTO SNPs used as IVs might be pleiotropic involved mental health phenotypes [e.g., subjective well-being (van den Broek et al., 2018) or phobic anxiety symptoms (Walter et al., 2015a), or common mental disorders (Kivimäki et al., 2011), including depression (Walter et al., 2015b)]. This evidence concerns the gene FTO and major depressive disorder.