Leptin has been shown to be involved in energy homeostasis and stress;30 however, emerging evidence has shown that structural and functional changes in the mesolimbic reward system are associated with reward-related behaviors, which involve hormonal regulators such as leptin, ghrelin and insulin.31, 32 In this study, the effects of endogenous leptin signaling on cocaine reward-associated behaviors and anxiety were detected. This evidence concerns the gene LEP and Anxiety.