Furthermore, given that DRD2 regulates the synthesis, release, and storage of dopamine [43], this decrease in DRD2 expression in female children may result in blunting of dopamine signaling and could explain the increase in susceptibility to mental health disorders (i.e., PTSD symptomology, anxiety, and depression) in female chronic pain patients [7,58,59,60,61,62]. This evidence concerns the gene DRD2 and major depressive disorder.