Leptin‐deficient mice displayed increased anxiety‐related behavior in the light–dark test.113 In addition, mice with LepRb selectively knocked out in dopamine neurons exhibited an anxiogenic‐like phenotype in approach‐avoidance testing.114, 115 Regarding fear, both systemic and intra‐amygdala injections of leptin impaired fear expression when injected before recall (Table 1).116. The gene discussed is LEP; the disease is Anxiety.