CD38 and major depressive disorder: Furthermore, as traumatic events may be a risk factor for suicidal behaviors (Dube et al., 2001; Seedat et al., 2005) and individuals who have experienced trauma displayed lower CSF oxytocin concentrations (Heim et al., 2008), we hypothesized that the relation between traumatic life events and depression suicidal ideation would be moderated by the OXTR and CD38 genotypes.