For example, though reduction in GABAergic transmission has been identified in FXS (Section “Upstream Regulators of mTORC1 Regulate Molecules at the PSD to Effect Changes in Synaptic Physiology”), use of a selective GABA-B receptor agonist arbaclofen showed limited improvements in social behaviors only in young but not older children and adults in a Phase 3 clinical trial (Berry-Kravis et al., 2017). Here, GABBR1 is linked to fragile X syndrome.