The causes of severe back pain at night but not during the day are as follows: 1. it may be due to infection of the lumbar spine or tuberculosis of the lumbar spine. 2. it may be due to tumors of the lumbar spine, especially metastatic tumors of the lumbar spine are more common. 3. it may be due to ankylosing spondylitis or problems caused by lesions of the lumbar spine, such as lumbar spondylolisthesis, lumbar spinal stenosis, lumbar disc herniation, etc. If this symptom lasts for a long time and there is no relief within a short period of time, you must go to a regular hospital in time to improve the MRI of the lumbar spine to clarify the severity of the disease, so as to choose a more reasonable treatment method and not to delay the condition.