In the overall level, the statistically correlation between OPRM1-A118G polymorphism and increased nicotine-dependence risks was not found in any of the five models (allele model: OR 1.000, 95% CI 0.906, 1.104; p = 0.999; Figure 3A; homozygote model: OR 1.032, 95% CI 0.771, 1.381; p = 0.834; Figure 3B; heterozygote model: OR 0.963, 95% CI 0.799, 1.162; p = 0.696; Figure 3-C; dominant model: OR 1.006, 95% CI 0.916, 1.104; p = 0.907; Figure 3D; recessive model: OR 0.967, 95% CI 0.715, 1.309; p = 0.830; Figure 3E). The gene discussed is OPRM1; the disease is substance dependence.