SV2A and major depressive disorder: Notably, the study of SV2A‐specific binding to synapses using 11C‐UCB‐J‐PET will allow us to examine synapses directly in vivo, and we expect that it will lead to the identification of a new objective marker or outcome measure of the efficacy of ketamine for treatment‐resistant depression, or of other clinical trials of therapies targeting synapse restoration.