Saliva samples were collected under researcher observation for DNA analyses using Oragene saliva collection kits. Genotyping was performed at the UCLA Genotyping and Sequencing (GenoSeq) Core. Polymerase chain reaction (PCR) primers were labeled with fluorescent dye (6-FAM, VIC or NED), and PCR was performed on Applied Biosystems dual block PCR thermal cyclers. SNP sequencing was run on an AB 7900HT Fast Real-Time PCR System and analyzed using the Sequence Detection Systems (SDS) software version 2.3. Each run included two positive control samples (individual 2 in CEPH family 1347; Coriell Institute). Genotypes were automatically scored by the allele calling software and verified by visual inspection. In process validation checks, the UCLA GenoSeq Core has average call, reproducibility, and concordance rates of 96%, 99.7%, and 99.8%, respectively. In the screening sample (n= 295), the following OPRM1 genotypes were observed: AA, n = 224, AG, n = 59, and GG, n = 10 (2 samples could not be genotyped). In the experimental sample (n = 43), prospectively genotyped for the OPRM1 A118G SNP, genotypes were: AA, n = 23, AG, n = 18,
