Preclinical studies should also investigate whether some of the mechanisms through which antipsychotics contribute to obesity, i.e. upregulation of neuropeptide Y and melanin-concentrating hormone, decreased expression of leptin-induced AMP-activated protein kinase, reduction of orexin, effects on α2 or muscarinic receptors [56], could also directly affect brain structure. The gene discussed is NPY; the disease is obesity due to melanocortin 4 receptor deficiency.