To estimate the effective number of independent tests corresponding to the six correlated discovery tests, we used matSpD [http://gump.qimr.edu.au/general/daleN/matSpD/], which accounts for correlations among phenotypes (Cheverud 2001; Li and Ji 2005; Nyholt 2004). Using Pearson correlations among the five dependence diagnoses from the studies with all five phenotypes assessed (see Table S3), plus one additional test for general substance dependence, we obtained a conservative estimate of 5.1218 independent tests, corresponding to a Bonferroni-corrected p-value threshold of α′ = 9.76 × 10−3 for statistical significance.
