Whereas, Akkus et al. reported no significance difference in [11C]ABP688 binding in individuals with schizophrenia compared with healthy controls (226), a multi-modal imaging approach, combining mGluR5 PET imaging with [11C]ABP688 together with fMRI reported a lower mGluR5 availability and related functional connectivity alterations in drug-naïve young adults with major depression (227). Here, GRM5 is linked to schizophrenia.