TPH2 and post-traumatic stress disorder: Functional polymorphisms of the TPH2 gene have repeatedly been found to be associated with depressive disorders (Gao et al., 2012; Zill et al., 2004), PTSD (Goenjian et al., 2012, 2015), and the personality trait harm avoidance (Reuter et al., 2007) which is negatively associated with resilience (Kim et al., 2013; Simeon et al., 2007).