Indeed, several studies showed beneficial effect of the MAO inhibitor, selegiline in AD (Tariot et al., 1987; Knoll et al., 1989; Sano et al., 1997), and dextroamphetamine, an inhibitor of MAO-A and MAO-B, is in Phase 4 clinical trial as a combination drug together with methylphenidate for AD treatment (Herrmann et al., 2008). This evidence concerns the gene MAOA and Alzheimer disease.