NPY and depressive disorder: Furthermore, significant changes in NPY-like immunoreactivity (NPY-ir) were observed not only in animal models of depressive disorders (Jiménez-Vasquez et al., 2000a,2000b; Wu et al. 2011) but also in depressed patients who presented reduced levels of NPY in the cerebrospinal fluid and plasma in several studies (Widerlöv et al. 1988; Westrin et al. 1999; Heilig et al. 2004; Soleimani et al. 2014).