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Schizophrenia is characterized by clinical heterogeneity and genetic heterogeneity. 1 Because dopamine(DA)overactivity has been thought, over the past 40 years, to play a role in the pathophysiology of schizophrenia, its receptors and metabolic enzymes have been regarded as potentially involved in schizophrenia. 2 However,disease-causing variants among the genes coding for dopamine receptors and the enzymes related to DA have not been found. Cholecystokinin A receptor (CCK-AR)coexists with DA in the same neurons of the midbrain limbic system, as well as the access to the substantia nigra and the corpus striatum, and it acts as a mediator modulating dopaminergic activity. 3 Two CCK receptors,CCK-AR and CCK B receptor (CCK-BR) have been identified. CCK-AR in the medial posterior nucleus accumbens increases DA release, while CCK-BR in the anterior nucleus accumbens decreases DA release. 4 The former has potential effects on human neuropsychiatric diseases linked to DA, such as schizophrenia. Recently,several studies found that the Pst I polymorphic site present in the boundary between intron 1 and exon 2 of the CCK-AR gene is associated with some symptoms of schizophrenia. This finding is particularly important for uncovering the genetic etiology of schizophrenia, although the mechanism linking this polymorphic site to the disease remains unclear. The present work is an attempt to confirm the genetic association between the CCK-AR gene and schizophrenia.