To reveal the associations of DNA methylation of TRPA1 with neuropathic pain and psychological variables, we examined neuropathic pain characteristics and psychological states, and measured the methylation rate at the promoter region of the TRPA1 gene, including CpG -51 in the whole blood of patients who suffered chronic pain or were scheduled to undergo thoracic surgery for lung cancer. The gene discussed is TRPA1; the disease is lung carcinoma.