Additionally, it has been suggested that polymorphisms in ADRA2A (alpha-2A adrenergic receptor), DRD3 (dopamine receptor D3), DBH (dopamine β-hydroxylase) and SNAP-25 (25 kDa synaptosomal-associated protein) are individually or collectively risk factors for schizophrenia [24–27]. This evidence concerns the gene DRD3 and schizophrenia.