In the sequencing stage, the coding regions and the flanking intronic regions of 17 genes associated with NMDARs were sequenced using DNA samples collected from 760 SD cases and 760 controls for a total of 1520 research subjects. The 760 SD cases all had lifetime diagnoses of dependence on three substances: alcohol, cocaine and opioids. Some SD subjects were also dependent on other drugs, such as nicotine and cannabis. The 760 controls were healthy subjects with no lifetime SD or substance abuse diagnoses. In addition to these 1520 subjects, another 6751 subjects were studied in the genotyping stage. Among them, 5482 had phenotype information for AD (1269 subjects who met criteria for alcohol abuse, but not for AD, were excluded from the analyses), 6538 had phenotype information for CD (213 subjects with cocaine abuse, but not CD, were excluded from analyses), and 6608 had phenotype information for OD (143 subjects with opioid abuse, but not OD, were excluded from analyses). None of these 8271 subjects had lifetime diagnoses of schizophrenia, schizoaffective disorder, or mental retardation.
