These studies include those that have examined the combined effects of 5-HTTLPR and BDNF alleles on behavioral traits (Jiménez-Treviño et al., 2019), brain structure and depression (Han et al., 2018), functional brain activity and emotional reactivity (Wang et al., 2012) and childhood adversity (Benedetti et al., 2017). The gene discussed is BDNF; the disease is major depressive disorder.