Additionally, the methylation level of CG2 in the KCNQ2 gene was significantly associated with methamphetamine dependence (p = 0.003), yielding an AUC of 0.68 (95% CI: 0.568–0.792), a sensitivity of 0.40 and a specificity of 0.92. The gene discussed is KCNQ2; the disease is methamphetamine dependence.