As illustrated in Figure 3, the methylation level of CG2 within the GABRB1 gene exhibited remarkable diagnostic significance for methamphetamine dependence (p = 6.47E−11), with an area under the ROC curve (AUC) of 0.902 (95% CI: 0.836–0.969), a sensitivity of 0.85 and a specificity of 0.88. This evidence concerns the gene GABRB1 and methamphetamine dependence.