Fig. 2. ARPA for the Spanish sample.

a Derived tree by CART for SUD status as categorical target variable (disjunctive affection status, i.e., substance use of either alcohol, or nicotine, or other drugs). This derived tree for the Spanish sample included demographic (sex), clinical (CD, ODD, depression, and ADHD), and genetic variables (markers rs677642, rs4860437, rs1868790). b Variable importance scores derived by Random Forest and TreeNet analysis were compatible with the variables included in the tree derived by CART. c, d TreeNet analysis to maximize the AUC and minimize the classification error using 200 trees. The AUC were 0.911 and 0.897 for learning and testing samples while the proportions of misclassification for SUD cases in the cross-validation experiment were 0.151 and 0.175 for learning and testing data sets, respectively. Conventions as in Fig. 1