SLC6A4 and autism: Our initial findings based on single concentration ligand binding studies in young adults with ASD provided strong evidence for alterations in brain 5‐HT systems in autism due to the high sensitivity of autoradiography methods, with reductions in density of 5‐HT1A and 5‐HT2A receptors in the PCC and fusiform gyrus (FG), but no change in binding to the transporter 5‐HTT (Oblak et al. 2013).