Hypertension is categorized into primary hypertension and secondary hypertension. The causes of primary hypertension are genetic, environmental, and other factors. The causes of secondary hypertension include kidney disease, endocrine disease and so on. 1. Primary hypertension (1) Genetic factors: if both parents have hypertension, the probability of the child developing the disease is as high as 46%. (2) Environmental factors: ① Diet: excessive salt intake, high protein intake are all pressure-raising factors, but potassium intake is negatively correlated with blood pressure. ② Mental stress: mental laborers, engaged in high mental tension occupations are more likely to develop high blood pressure. ③ Smoking: Smoking can make the sympathetic nerve endings release norepinephrine, thus increasing blood pressure. (3) Other factors: ① weight: weight gain is an important risk factor for elevated blood pressure. (② Drugs: contraceptive pills, ephedrine, non-steroidal anti-inflammatory drugs, licorice, etc. can increase blood pressure. ③ Sleep apnea hypoventilation syndrome: 50% of patients with sleep apnea hypoventilation syndrome have hypertension. 2. Secondary hypertension (1) Renal diseases: such as renal artery stenosis, glomerulonephritis, polycystic kidney, renal tumor and so on. (2) Endocrine diseases: such as pheochromocytoma, primary aldosteronism, etc. (3) Cardiovascular lesions: such as aortic valve insufficiency, polyarteritis, etc. (4) Craniocerebral lesions: such as traumatic brain injury, brain tumor, brainstem infection, etc. (5) Others: e.g. erythrocytosis, hypertensive syndrome of pregnancy, etc. Patients with hypertension should go to the hospital to find out the cause and standardize the medication.