8 min read
Cecily Grace Morgan
Slowly but surely, medical cannabis prescriptions are becoming more accessible in the UK. A growing body of research indicates that cannabis-based medicines may help some patients manage a wide range of conditions, from anxiety and post-traumatic stress disorder to chronic pain and epilepsy.
However, when considering the use of cannabis-based medicines, prescribers should be aware of how they could affect other aspects of health. For example, the potential links between medical cannabis and hypertension.
Key takeaways
Contents
Blood pressure is the force with which blood moves through the body. It is created by the heart as it pushes blood out through contraction and by the differences in pressure between the heart and smaller blood vessels.
Blood pressure is a vital bodily function, responsible for moving blood (and the nutrients, oxygen, and white blood cells within) to the different areas of the body. It is also essential in carrying waste products through the liver and kidneys.
Blood pressure is measured using two numbers (e.g., 120/80). These numbers represent the systolic pressure (the top number) and the diastolic pressure (the bottom number).
“Normal” blood pressure can depend on a number of factors; however, according to the British Heart Foundation, it is usually considered to be between 90/60 mmHg and 120/80 mmHg for people below the age of 80. For those aged 80 years and older, the ideal blood pressure is considered to be lower than 150/90 mm Hg.
High blood pressure is considered to be a reading of 140/90 mmHg or higher. Also known as hypertension, it is a serious cause of premature death worldwide.
When blood pressure is too high, it places extra strain on the heart, blood vessels, and other organs, including the brain, kidneys, and eyes. This can increase the risk of a number of other serious health conditions, including:
Heart disease
Heart attacks and strokes
Heart failure
Peripheral arterial disease
Kidney disease
Vascular dementia
Hypertension can also cause a number of other symptoms, such as nosebleeds, morning headaches, vision changes, and buzzing in the ears. However, most people with high blood pressure actually have no symptoms, so it’s important to check it regularly, even if you feel fine.
A number of factors have been linked to raised blood pressure, including lifestyle choices, such as having a poor diet (being overweight, not eating enough fruit and vegetables, eating too much salt), not doing enough exercise, drinking large amounts of alcohol and smoking.
Genetics and age have also been linked to high blood pressure. Being over the age of 65 or having a relative with high blood pressure could put you at higher risk of having it. The condition is also more prevalent in people of Black African and Caribbean descent and those living in deprived areas.
Some people may have low blood pressure, considered to be a reading of less than 90/60 mmHg. While low blood pressure (hypotension) doesn’t always cause symptoms, it may require treatment when it does. Symptoms can include:
Dizziness or lightheadedness
Feeling sick or weak
Blurred vision
Fainting
Confusion
Like high blood pressure, low blood pressure can be associated with certain medical conditions, such as diabetes, as well as some medicines. If medication is the cause of hypotension, your doctor may alter your dose or change your medicine. Blood pressure can also become lower during pregnancy.
The link between cannabis and blood pressure is still unclear. While some studies indicate that cannabis use may raise blood pressure, others suggest the opposite may be true. However, more recent studies suggest that the answer may not be straightforward either way.
As we’ve mentioned, dizziness or lightheadedness are symptoms of low blood pressure. However, they’re also known side-effects of the THC in medical cannabis, with some patients feeling dizzy or lightheaded when they stand up quickly. If this happens, sit or lie down until it passes and inform your prescriber.
Some research suggests that THC, the most common psychoactive compound found in the cannabis plant, may cause an immediate increase in blood pressure. This may be linked to an increased risk of heart attack immediately after cannabis use, particularly in people with existing heart problems.
However, much of the current evidence linking cannabis use to cardiovascular problems is based on reports from individuals who smoke the drug. This makes it hard to separate the effects of carcinogens and irritants that may be present in cannabis smoke, which is often consumed alongside tobacco, from the effects of cannabinoids and other active cannabis compounds.
Several studies have indicated that long-term cannabis use may be associated with lowered blood pressure. For example, a 2023 study assessed questionnaire responses from 91,161 UK citizens from the UK Biobank to examine gender-stratified associations between cannabis use and blood pressure levels.
They found that lifetime heavy cannabis use was associated with decreases in systolic and diastolic blood pressure, and pulse pressure in both men and women. However, the authors of the study note that the differences in blood pressure between heavy cannabis users and “never users” were too small to recommend adopting cannabis therapy for blood pressure modulation into clinical practice.
A small 2021 study found similar effects. Among older adults, medical cannabis use was associated with a reduction in 24-hour systolic and diastolic blood pressure following three months of treatment.
There’s no good evidence that CBD oil raises blood pressure and a 2017 crossover study found that, compared to a placebo, a single dose of CBD reduced resting blood pressure, as well as blood pressure increases due to stress in healthy volunteers. While this is hopeful, much more research into CBD oil and hypertension is needed to determine whether this effect could be clinically useful for patients.
That totally depends on the type of medication, how stable your blood pressure is and medical history. At Releaf, our clinicians take all these factors into account when assessing eligibility for medical cannabis and creating a treatment plan. They understand the potential links between hypertension and medical cannabis and will treat and advise patients accordingly.
Certain blood pressure medications shouldn’t be combined with CBD or medical cannabis, so you must always consult a doctor before consuming any CBD or medical cannabis.
Hypertension, or high blood pressure, can have various causes. However, the three main reasons for developing high blood pressure are unhealthy lifestyle choices (smoking, heavy alcohol intake, a sedentary lifestyle, etc.), genetic predisposition, and underlying health conditions such as kidney disease or sleep apnoea.
Vasodilation is the widening of blood vessels, which can lower blood pressure. Cannabinoids (CBD, THC) interact with receptors in the body's endocannabinoid system, which plays a role in cardiovascular function. When activated, these receptors can cause vasodilation, and CBD's anti-inflammatory properties may also contribute to lowering blood pressure.
Evidence is limited on cannabis and blood pressure. The 2021 study mentioned earlier suggests that cannabis may create a drop in blood pressure that reaches its lowest level at around 3 hours after consumption, before it begins to rise again. However, much more research is needed to determine how long the effects last.
There is some evidence to suggest that CBD can raise your heart rate. The 2017 study mentioned earlier indicated that CBD might lower blood pressure and raise heart rate slightly, but much more research is needed to make a strong link. THC has also been shown to raise heart rate in some people. Therefore, medical cannabis is often not recommended for those with cardiovascular conditions.
CBD shouldn’t be consumed by people who are pregnant, breastfeeding or trying to conceive, and children and teens shouldn’t take CBD unless prescribed by a specialist. What’s more, people on certain medications that can interact with medical cannabis, including common blood thinners, thyroid medications, and seizure medications, should avoid CBD.
Even if you don’t fall into these categories, it’s important that you seek medical advice before taking CBD.
Research into the effects of cannabis on blood pressure is expanding; however, more evidence is required to understand how the effects of different cannabinoids and consumption methods may vary. Furthermore, the mechanisms through which cannabis may impact blood pressure and cardiovascular health require further assessment.
While current evidence indicates that long-term cannabis use may be associated with a reduction in blood pressure, it remains vital that healthcare providers continue to monitor blood pressure and other factors throughout patients’ treatment to ensure the effective use of cannabis-based medicines.
If you’re curious about medical cannabis and whether it could be an option for you, our online eligibility checker is fast and free.
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We are proud to announce a new partnership between Releaf and brainstrust, the UK charity supporting people affected by a brain tumour. Together, we want to make sure that anyone living with a brain tumour has access to compassionate, expert care through the most trusted medical cannabis clinic in the UK. Here is what the partnership means and how patients currently in treatment can get in touch.
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