This study investigated the possible association between three functional polymorphisms in the promoter region of the dopamine D4 receptor ( DRD4 ) gene and schizophrenia , depression , and heroin addiction .
O O O O O O O O O O O O O O O O B-GeneOrGeneProduct I-GeneOrGeneProduct I-GeneOrGeneProduct O B-GeneOrGeneProduct O O O B-DiseaseOrPhenotypicFeature O B-DiseaseOrPhenotypicFeature O O B-DiseaseOrPhenotypicFeature I-DiseaseOrPhenotypicFeature O