SNPs in the region of the nicotinic receptor clusters on chromosomes 8 and 15 were tested for association with the scaled scores of neuropsychological phenotypes in European-Americans from the COGA study using an additive linear mixed effects (LME) model with the lmepack.batch function as implemented in the GWAF package in R using age, sex and FTND score as covariates [39]. Neither alcohol nor cocaine symptom count were significant covariates in the analysis and were thus not included in the analysis. The GWAF package enables association testing with the ability to include individuals from families by correcting for relatedness specified in a pedigree file.
