In light of this view, and the biological importance of FMRP and CYFIP1 at the synapse (outlined in sections “Synaptic FMRP: Regulator of mRNA and Local Translation” and “Synaptic CYFIP1: A Negative Regulator of Protein Synthesis and Cytoskeletal Dynamics”), we will now consider the role of FMRP and CYFIP1 in the aetiology of psychiatric disorders, using data from human patient studies, especially psychiatric genomics, and preclinical models. Here, CYFIP1 is linked to psychiatric disorder.