HTR2A and schizophrenia: In studies on samples of patients with schizophrenia, it was shown that schizophrenia patients more often carry the major genotype C/C of the HTR2A gene to a statistically significant extent (this corresponds to G/G, since the loci rs6313 C>T and rs6311 G>A are in non-equilibrium coupling), while having a low density of serotonin 2A receptors in the brain (Polesskaya et al., 2002; Parsons et al., 2004).