Three studies have shown a significant decrease in serum [80,81] or plasma [82] aSyn levels in children diagnosed with autism spectrum disorders compared with controls, one of them also found decreased serum aSyn levels and alpha-synuclein (SNCA) gene expression in mothers of patients with autism [82], and other increased plasma beta-synuclein (bSyn) levels in patients with autism [82]. This evidence concerns the gene SNCA and autism spectrum disorder.