Last, but not least, dysregulated circadian rhythms have been associated with the development of both mental [22, 23] and metabolic disorders [24, 25], and, interestingly, altered circadian rhythms are connected with impaired biological functions of several possible mediators of the comorbidity of mental and metabolic disorders, including glucocorticoids [26], insulin [27], leptin [28] and adult hippocampal neurogenesis [29, 30]. This evidence concerns the gene LEP and metabolic disease.