Krzystanek et al. (2021) did not find any associations between selected nucleotide variants in GRIN1, GRIN2A, and GRIN2B and resistance to clozapine and the presence of cognitive deficits in schizophrenia in a targeted group of 45 Polish patients with super clozapine-resistant schizophrenia and cognitive impairment [30]. The gene discussed is GRIN2B; the disease is Cognitive impairment.