GRM2 and major depressive disorder: In fact, mGlu2/3 receptors have been linked to anxiety, schizophrenia, depression, chronic pain, drug addiction, and neurodegenerative disorders (Nicoletti et al., 2011; Planas-Fontanez et al., 2020; Abd-Elrahman et al., 2021; Li et al., 2022; Mazzo et al., 2022; Turati et al., 2022).