Emotional disorders such as depression, generalized anxiety disorder and PTSD in humans have been shown to be associated with altered peripheral BDNF levels (Fernandes et al.2014; Matsuoka et al.2013; Wang et al.2015), and these peripheral levels are in turn postulated to reflect central BDNF signaling which is assumed to influence brain function. The gene discussed is BDNF; the disease is depressive symptom measurement.