DRD2 and schizophrenia: Previous studies which includes the autopsy results of patients with schizophrenia (Camps, Cortes, Gueye, Probst, & Palacios, 1989; Hess, Bracha, Kleinman, & Creese, 1987), findings from PET studies (Breier et al., 1997; Laruelle et al., 1996, 1997), and pharmacological evidence (Seeman, 2002; Worrel, Marken, Beckman, & Ruehter, 2000) suggested a close relationship for DRD2 gene and schizophrenia.