One of the assumed pathogeneses of this late-onset treatment-resistant schizophrenia (TRS) is antipsychotic-induced dopamine supersensitivity psychosis (Ai-DSP), which may be associated with compensatory upregulation of dopamine D2 receptors (DRD2) due to over-blockade by antipsychotics [9–12]. This evidence concerns the gene DRD2 and psychotic disorder.