The nightmares often occur due to the following factors: 1) Inadequate blood supply to the cerebral arteries, often due to stenosis or plaque in the vertebral basilar artery and internal carotid artery system, resulting in inadequate blood supply to the cerebral arteries and causing transient cerebral ischemia during sleep, resulting in nightmares. 2) Phytodysfunction, especially in patients with severe phytodysfunction such as insomnia, anxiety, and forgetfulness. The most common cause of nightmares is a severe decrease in the deep sleep phase and an increase in the light sleep phase. 3. nightmares can occur when the brain is deprived of oxygen, such as increased intracranial pressure, pulmonary hypertension, and pulmonary hypoplasia, which leads to hypoxia. 4. nightmares can also occur in patients with abnormal brain cell discharges due to substantial cerebrovascular diseases, such as epilepsy and convulsions.