Some cardiovascular effects of marihuana smoking in normal volunteers

Abstract

Marihuana smoking caused a significant increase in heart rate in 25 normal male volunteers. The degree of techycardia was significantly related to the dose of Δ‐9‐ tetrahydrocannabinol (Δ‐9‐THC). The marihuana smoked contained 0.5 and 2.9 per cent Δ‐9‐THC and was compared to extracted marihuana as a control in a single‐blind experimental design. Dose of Δ‐9‐THC was expressed as the total amount available in the number of cigarettes smoked under standard conditions. The tachycardia reached a maximum within 30 minutes and persisted longer than 90 minutes. Systolic and diastolic blood pressures were significantly elevated after total doses of marihuana containing more than 10 mg. of THC, but blood pressure was better correlated to heart rate than to dose. Changes in the electrocardiogram were minimal, but there were premature ventricular contractions in some subjects.