The values of phenotype variables range from 0 to 7. Figure 2 shows the frequency distributions of the 4 phenotype variables. Since they are not normally distributed, we calculated their correlations using the Kendall rank correlation. Table 3 shows moderate correlations ranged from 0.34 to 0.51. Table 3The Kendall rank pairwise correlations between alcohol, nicotine, marijuana, and cocaine outcomesAlcoholNicotineMarijuanaCocaineAlcohol10.45540.42360.5029Nicotine10.33730.3375Marijuana10.5067Cocaine1
