The most important thing: THC increases the heart rate by 20-50 bpm by activating the sympathetic nervous system. In healthy boys: harmless. In coronary heart disease: risk of heart attack increases 4.8-fold in the first hour. CBD, on the other hand, lowers blood pressure.
At a glance:
THC increases the heart rate by 20-50 bpm through direct sympathetic activation
Risk of heart attack in the first hour after consumption: 4.8 times higher (Mittleman 2001)
CBD has the opposite effect: lowers the resting heart rate and systolic blood pressure
Cannabis has measurable effects on the cardiovascular system – mainly through THC, not CBD. For most healthy adults, these effects are temporary and harmless. However, they can be clinically relevant for people with existing heart disease, high blood pressure or cardiac arrhythmia.
Cardiovascular effects of THC
Effect
Mechanism
Time course
Clinical relevance
Tachycardia (+20-50 bpm)
Sympathetic activation via CB1; inhibition of the parasympathetic nervous system
Mittleman et al. 2001 (Circulation): Case-crossover study, n=3882 myocardial infarction patients. Risk of myocardial infarction in the first hour after cannabis use: 4.8-fold increased vs. non-use. Absolute risk, however, very low in young healthy people; mainly relevant in the case of pre-existing CHD.
Jouanjus et al. 2014 (J Am Heart Assoc): Analysis of 1979 cases from the French pharmacovigilance system. For cannabis-associated heart problems: 85 % male, average age 34 years. Atrial fibrillation and coronary events overrepresented.
Singh et al. 2018 (J Am Coll Cardiol, Review): Chronic use: increased rate of atherosclerosis due to proinflammatory effects of high-dose THC ingestion. Acute effects (tachycardia) in old age or with pre-existing CHD = main risk factor.
CBD and the heart: Rather positive
In contrast to THC, CBD has cardioprotective properties:
– Antiarrhythmic: CBD reduces ischemia-induced arrhythmias in animal models
– Vasodilating: CBD relaxes blood vessels via TRPV1 and NO release → lowers blood pressure
– Anti-inflammatory: Atherosclerosis is driven by inflammation; CBD has an inhibitory effect
– Manseau et al. 2019: CBD (600 mg once) significantly reduced the increase in blood pressure during stress reactions in RCTs
Study highlight: Mittleman 2001 (Circulation, n=3882): Heart attack risk increased 4.8-fold in the first hour after cannabis use. Absolute risk in healthy individuals low – clinically relevant and not to be ignored in the case of pre-existing CHD.
Risk groups: Who should be careful
– People with coronary heart disease (CHD)
– Cardiac arrhythmia (atrial fibrillation)
– Uncontrolled hypertension
– Heart failure
– Elderly patients (>65 years)
– People on heart medication (digoxin, blood thinners, beta-blockers)
THC increases heart rate by 20-50 bpm and oxygen demand – harmless in healthy boys, clinically relevant in CHD or arrhythmias (4.8-fold increased risk of heart attack in the first hour, Mittleman 2001). CBD, on the other hand, shows cardioprotective properties (antiarrhythmic, antihypertensive). Risk groups: CHD, atrial fibrillation, heart failure, hypertension, cardiac medication. Cannabis and alcohol for further combination risks; cannabis-drug interactions for cardiovascular medications.
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