Essential hypertension, which is also called primary hypertension, is high blood pressure in which the exact cause is unknown, as explained by Mayo Clinic. Essential hypertension can develop slowly over time. In the United States, approximately 95 percent of all high blood pressure cases have unidentifiable causes, according to WebMD.
Although primary hypertension may be idiopathic in nature, there can be some risk factors that may contribute to its development, such as a family history of hypertension, age, gender and race, as stated by WebMD. Another influencing factor is a high intake of salt in a diet.
Hypertension is defined as having a blood pressure that is above the normal range of 120 over 80, where the upper number is systolic pressure and the lower number is diastolic pressure. There are different stages of hypertension, including pre-hypertension, stage 1 and stage 2. Pre-hypertension is a blood pressure reading in which the systolic pressure is between 120 to 139 and diastolic pressure is in the range of 80 to 89.