Cannabis remains the world’s most widely used controlled substance, and the prevalence of consumption has grown steadily as legal and cultural attitudes have shifted. But as access to both non-medicinal and medicinal cannabis products expands, it is important to understand the associations between consumption and public health.
In a recent study, published in Nutrition, Metabolism, and Cardiovascular Diseases, researchers aimed to understand the potential links between cannabis use and the risk of metabolic disorders.
What is metabolic disease?
Metabolic disease is a group of long-term health conditions. They affect how the body uses energy, sugar, and fat.
The main conditions in this group are:
- High blood pressure (hypertension)
- Type 2 diabetes
- Raised cholesterol
- Obesity
- Non-alcoholic fatty liver disease
These conditions often happen together. Together, they raise the risk of heart attacks and strokes. The number of people living with metabolic disease is rising around the world. This is why doctors and researchers want to understand what may raise or lower the risk.
What did the new UK study look at?
The study used data from the UK Biobank. The UK Biobank is a long-term health study. It follows the lives of more than 500,000 adults across the UK. Most joined the study between 2006 and 2010.
In October 2016, around 157,000 of these adults answered an online questionnaire. The questionnaire asked whether they had ever used cannabis in their lives. The researchers used this answer as their starting point.
The team then left out anyone who already had a metabolic condition. They also left out people with missing details. This left around 91,000 adults. Their health was followed for up to seven years.
To pick up new diagnoses, the team used GP records, hospital records, and death registers.
How did the study group cannabis use?
Researchers grouped people in two ways.
By how often they had used cannabis in their lifetime:
- Low use: 1 to 10 times.
- Moderate use: 11 to 100 times.
- Heavy use: more than 100 times.
By when they had last used it:
- Current users: had used cannabis within the last year.
- Past users: had used cannabis, but not within the last year.
People who had never used cannabis made up the comparison group.
Were there any associations between cannabis use and metabolic disorders?
Around one in four adults (~23,000) in the study said they had ever used cannabis. These adults tended to be younger. They were more often men. They were also more likely to have smoked tobacco than people who had never used cannabis.
Cannabis consumers were more likely to have a college or university degree and reported higher income levels.
The researchers then took into account things that affect health. These included age, sex, smoking, drinking, income, and education. After this, they reported small differences:
- Ever-users appeared to have a slightly lower risk of metabolic disease overall.
- They appeared to have a slightly lower risk of high blood pressure.
- They appeared to have a slightly lower risk of type 2 diabetes.
- People who said they had used cannabis heavily over their lifetime appeared less likely to develop obesity.
- No clear link was seen for raised cholesterol or fatty liver disease.
These differences were small. Many were close to the line where there is no real difference. This matters when interpreting the findings.
Why does body weight matter?
This is the most interesting part of the study. The picture changed depending on body weight.
Body mass index, or BMI, is a way of measuring weight in relation to height. The researchers split people into three BMI groups:
- Under 25, the healthy weight range.
- 25 to 30, the overweight range.
- Over 30, the obesity range.
In the healthy weight group, cannabis use was linked to a slightly lower risk of some metabolic conditions.
In the obesity group, the picture flipped. Moderate cannabis use in this group was linked to a possible higher risk of metabolic disease and high blood pressure.
Why might this be?
The body has a natural signalling system that responds to cannabis-like chemicals. The researchers think this system may already work differently in people living with obesity. This could be why the same exposure seemed linked to different patterns. This is one possible explanation. It has not been proven.
What do these findings tell us?
These findings indicate associations between cannabis use and the risk of metabolic disease outcome, in particular type 2 diabetes and hypertension.
Moreover, the researchers observed associations between cannabis use and BMI, which were more pronounced among normal-weight participants and weakened among those with obesity. Indeed, in participants with BMI >30kg/m2, moderate cannabis use was associated with an increased risk of metabolic disease.
What were the limitations of this study?
No single study tells us the full picture. This one is no different. Six points are worth keeping in mind:
- It is observational. It can only show patterns. It cannot prove cause and effect.
- Cannabis use was self-reported on a single questionnaire. People may not always remember accurately.
- The study only asked about lifetime use. It did not record dose, type of cannabis, or how it was used.
- It was not a study of prescribed medical cannabis. The findings cannot be applied to prescribed treatment.
- Most participants were older White European adults. The findings may not apply to everyone.
- A separate genetic study did not find evidence that cannabis use causes lower diabetes risk.
The point about prescribed medical cannabis is the most important one for our patients. The UK Biobank questionnaire asked about general cannabis use over a lifetime. It did not ask about cannabis prescribed by a doctor. The findings cannot be used to draw conclusions about prescribed treatment, given the inherent differences between legally prescribed, regulated medical cannabis and illegally-sourced cannabis.
What does this mean for patients?
On its own, not very much. The differences the researchers reported were small. The study cannot prove cause and effect. And it was not about prescribed treatment.
What it does add is a useful piece of background. It shows that the link between cannabis use and metabolic health is more complex than simple “good” or “bad” headlines suggest. Body weight, lifestyle, and many other factors all play a part.
If you have questions about your own metabolic health, the best step is to speak to a healthcare professional. They can look at your full medical history and lifestyle. They can also point you towards trusted advice. The NHS website is a good starting point for general information about high blood pressure, type 2 diabetes, and weight management.
Speak to a Curaleaf Clinic specialist
Curaleaf Clinic offers consultations to patients living with a range of long-term conditions that have not responded to first-line treatments. If you would like to speak to a specialist about your health, you can complete our eligibility check to see whether a consultation might be suitable for you.
