Marijuana does have the potential to lower blood pressure in the majority of cases. According to most studies, it causes a relaxed state that significantly reduces blood pressure, especially in those who are typically very stressed or tense. Although there is a risk for it to increase blood pressure, this is only a minor risk relevant to a few cases.
While marijuana has a calming effect on the body, blood pressure actually rises when under the influence of the drug. Depending on the potency and dose of the drug, blood pressure can spike drastically or very little. This usually lasts a couple of hours until it returns to normal. Chronically, there is a possibility for low blood pressure but only time will tell on that one.
The argument that marijuana can lower blood pressure had not been studied extensively because its use is outlawed in most states. The evidence that is there offers conflicting claims. Some data says that it actually raises blood pressure. Some claims cite the tolerance and health condition of the user. Therefore, it is impossible to make this blanket claim.
The use of marijuana does not lower blood pressure, according to both the Mayo Clinic and the National Institutes of Health. In fact, marijuana raises blood pressure and increases the heart rate of most users. Higher blood pressure, and increased heart rate, persist for three to four hours after ingesting marijuana.