Energy homeostasis is controlled by a complex neuroendocrine system consisting of peripheral signals, such as leptin, and central signals, particularly neuropeptides. Animal experiments have demonstrated that neuropeptides present in the hypothalamus and other brain areas are important not only in the regulation of feeding and metabolism, but also in other neuroendocrine and behavioural functions. Knowledge about neuropeptides is increasingly used in the study of the pathophysiology of behavioural disorders. This review focuses on the influence of polymorphisms in genes encoding neuropeptides or neuropeptide receptors involved in diverse physiological processes. The identification of neuropeptide systems closely associated with human illnesses will aid the development of novel therapeutic strategies.