for possible subsequent validation. Five SNP pairs were identified in AAs, including one that was strongly associated with DSM-IV CD and Group 4 (heavy cocaine use with infrequent intravenous injection), one associated only with Group 4 and three that were associated with Group 5 (early-onset, heavy cocaine use, high comorbidity). The association of a SNP pair comprised of one variant each from GRM1 and OPRM1 with Group 5 was nominally significant (P=7.6E–06), but exceeded the empirical threshold (P < 7.6E–07). Three pairs showed nominal significance in EAs as well, including two with Group 4 and one with Group 5. No SNP pairs were nominally associated with the DSM-IV diagnosis of CD. A SNP pair with variants from CRHR2 and BDNF was nominally significant for Group 4 after multiple test correction (P=3.5E–06), but it also exceeded the empirical threshold (P< 1.6E–6). Despite the fact that none of the results reached statistical significance when corrected for multiple comparisons, the findings in Table VI show that the two derived subtypes provide more statistical power for association analysis than the DSM-IV diagnosis of CD.
