TPH2 and Anxiety: Moreover, the importance of nongenetic factors in this context is illustrated by the observations that chronic restraint stress, maternal deprivation during early life combined with social defeat at adulthood, and neonatal administration of lipopolysaccharides are all interventions that produce both anxiety-like behavior in the EPM and elevated TPH2 expression in rodents (Chamas et al., 1999; Gardner et al., 2009; Sidor et al., 2010).