These observations strongly suggest that the -120-bp duplication polymorphism of DRD4 is associated with schizophrenia and that the -521 C/T polymorphism is associated with heroin addiction .
O O O O O O B-SequenceVariant I-SequenceVariant O O B-GeneOrGeneProduct O O O B-DiseaseOrPhenotypicFeature O O O B-SequenceVariant I-SequenceVariant O O O O B-DiseaseOrPhenotypicFeature I-DiseaseOrPhenotypicFeature O