Diabetes is the term for a group of related metabolic disorders characterized by prolonged high blood glucose levels. Diabetes affects over 420 million people worldwide (2014), resulting in millions of deaths per year–and its prevalence is rising. Substantial evidence indicates that cannabis may help to prevent and treat the disease.

There are 2 main types of diabetes:

1. Type 1 occurs when immune system attacks and destroys the insulin-producing beta cells of the pancreas, and insulin injections are needed. The cause is unknown, and it can occur at any age.
2. Type 2, when the body doesn’t use insulin effectively. Type 2 diabetes is more common than type 1. There are several known causes of type 2 diabetes, of which genetics and lifestyle are the most important ones. Type 2 diabetes mainly occurs in adults, but is increasingly diagnosed in children.

1. Cannabis may be preventative for diabetes

Diabetes is associated with high levels of fasting insulin and insulin resistance, as well as low levels of high-density lipoprotein cholesterol (HDL-C). In 2013, the results of a five-year study into the effects of cannabis on fasting insulin and insulin resistance were published in the American Journal of Medicine. Of the 4,657 respondents, 2,554 had used cannabis in their lifetime (579 were current users and 1,975 were past users) and 2,103 had never used the drug.

The researchers found that current users of cannabis had 16% lower fasting insulin levels than respondents who had never used cannabis, as well as having 17% lower levels of insulin resistance and higher levels of HDL-C. Respondents who had used cannabis in their lifetime but were not current users showed similar but less pronounced associations, indicating that the protective effect of cannabis fades with time.

The researchers also ran analyses on the data that excluded individuals diagnosed with diabetes. Even after excluding diabetics, current cannabis users were found to exhibit reduced fasting insulin and insulin resistance levels, indicating that cannabis can help prevent the occurrence of diabetes as well as controlling symptoms in diagnosed cases.

2. Cannabis lowers insulin resistance

Insulin resistance (IR) is a condition that causes cells to reject the normal mechanism of insulin, a hormone that is produced by the pancreas and is fundamental to the regulation of glucose metabolism. IR is associated with type 2 diabetes. In type 1 diabetes, the body is unable to produce insulin, while in type 2, insulin production is unaffected, but the cells are unable to process it.

When cells become insulin-resistant, they are unable to absorb the glucose needed to supply them with energy, and the unused glucose builds up in the bloodstream, leading to hyperglycemia.

The authors of the 2013 study found that current users of cannabis had a mean IR of 1.8, compared to 2.2 for past users and 2.5 for those that had never used cannabis. Current cannabis users were also found to have lower levels of blood glucose compared to past users and non-users. Current users had mean blood glucose levels of 99.7 mg/dL, compared with 100.6 mg/dL for past users and 103.5 mg/dL for non-users. However, the precise mechanism via which cannabinoids exert their effects on IR has thus far not been determined.

3. Cannabis helps to prevent obesity

Obesity, high body mass index (BMI) and large waist circumference are all linked to type 2 diabetes risk. Various studies have been conducted on the relationship between cannabis use and BMI, with conflicting results. A 2005 study on young adults found that cannabis use was not associated with higher BMI levels, whereas two large national surveys found slightly lower BMI and decreased levels of obesity in cannabis users despite higher-than-average daily consumption of calories. The 2013 study discussed earlier found that current cannabis use was associated with smaller waist circumferences than in past or non-users.

While the mechanism underlying the complex relationship between the endocannabinoid system, obesity and diabetes has not been fully established, a 2012 study demonstrated that obese rats lost significant weight and experienced an increase in pancreas weight after exposure to organic cannabis extract.

The increase in the weight of the pancreas indicates that the beta cells of the pancreas (which are responsible for the production of insulin) are protected by the presence of cannabinoids. In type 1 diabetes, the beta cells are destroyed by an autoimmune response, so providing protection to them may help to control the disease.

4. Cannabis may treat diabetes-induced neuropathy

People with diabetes often experience nerve disorders as a result of their disease. Nerve damage often affects the peripheries such as the hands and feet, but may occur in any organ or region of the body. The damage may be symptomless, but in many cases, pain, tingling and numbness accompany the disorder. As with many forms of nerve pain, diabetic neuropathy can be hard to treat with conventional analgesics. However, there is evidence to indicate that cannabis may have a role to play here too.

A study published in 2009 investigated the antinociceptive (pain-reducing) effects of cannabidiol extract in cases of diabetes-induced neuropathy in rats. The authors found that repeated administration of CBD extract “significantly relieved” mechanical allodynia (painful response to non-painful stimuli) and restored normal perception of pain without inducing hyperglycemia.

The treatment was also found to protect the liver against oxidative stress (which is believed to be a major contributing factor to developing neuropathy) and increase levels of nerve growth factor to normal levels.

However, studies on humans have thus far yielded less positive results. Also in 2009, a randomized controlled trial investigated the ability of GW Pharmaceuticals’ Sativex spray to ameliorate the symptoms of diabetic peripheral neuropathy. 30 subjects were administered with either Sativex or placebo. Pain scores improved significantly across the board, but the effect of Sativex was not found to be significantly greater than that of the placebo.

5. Cannabis may treat diabetic retinopathy

Up to 80% of diabetes patients that have had the disease for over a decade acquire a complication known as diabetic retinopathy (DRP), in which the cells of the retina are progressively damaged. This condition is responsible for approximately 5% of new cases of blindness each year in the USA.

It is thought that the pro-inflammatory immune response and oxidative stress processes have a key role to play in the breakdown of retinal cells. There is evidence that cannabidiol, with its known ability to combat both oxidative stress and inflammation, may be useful in treating the disorder.

In a 2006 study published in the American Journal of Pathology, diabetic rats were administered with CBD and tested to determine the rate of retinal cell death. It was shown that treatment with CBD significantly reduced oxidative stress and neurotoxicity and protected against retinal cell death and the breakdown of the bood-retinal barrier. This included reducing levels of tumour-necrosis factor-alpha (TNFα), a substance that is known to be involved in the inflammatory response.

Although mainstream and stereotypical thought about cannabis users would suggest that cannabis may have a negative effect on BMI, the waistline and diabetes, scientific evidence suggests otherwise. Overall, cannabis users are associated with lower risk of diabetes and lower risk of obesity, one of the leading causes of type 2 diabetes.