Lung cancer patient’s slow response is considered to be caused by cancer cells metastasizing to the brain, and it may also be caused by lung cancer patient’s complication of depression, Alzheimer’s disease and other diseases. 1. Metastasis of cancer cells: when lung cancer patients have slow reaction, it may be due to metastasis of cancer cells, and when metastasized to the brain, it will invade the nerve center of the brain of the patients, thus leading to slow reaction of the patients. 2. Depression: the pathogenesis and etiology of depression are not yet clear, and it is considered to be caused by biochemical and neuroendocrine factors. The main symptoms of patients are low mood, slow thinking, anxiety and self-blame and self-guilt, etc. If lung cancer patients are complicated with depression, it will lead to the phenomenon of slow reaction of patients. 3. Alzheimer’s disease: Alzheimer’s disease is mostly caused by genes, life style and environment. Patients will have symptoms such as impaired memory, attention and executive ability, and in serious cases, aphasia and dysarthria, etc. If lung cancer patients are accompanied by Alzheimer’s disease, they will also have slow reaction. 4. Others: If lung cancer patients are complicated with other diseases such as anxiety disorder and heart disease, it may also lead to slow response. When lung cancer patients have symptoms of slow reaction, they should consult doctor in time and follow doctor’s advice.