Lifelong and current users of marijuana - those "who reported using marijuana in excess of 100 times by young adulthood" - may greatly increase their risk of developing prediabetes, according to a new study.

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Marijuana use greatly increases chances of developing prediabetes, a new study shows.

A new study published in Diabetologia reports that current and former users of marijuana are more likely to develop poor blood sugar control, known as "prediabetes," than those who never used marijuana.

A link has not been established, however, between marijuana use and full-blown type 2 diabetes - the most common form of diabetes - say the researchers, from the University of Minnesota School of Public Health in Minneapolis.

According to the 2013 National Survey on Drug Use and Health, marijuana is the most commonly used illicit drug in the US, at 19.8 million past-month users.

Marijuana potency is on the increase - it has risen steadily over the past few decades. Previous studies have linked use of the drug to a wide range of acute, long-term and persistent adverse effects.

Mike Bancks, of the University of Minnesota School of Public Health and a postdoctoral cardiovascular trainee at the National Heart, Lung and Blood Institute at the National Institutes of Health, led the research team.

They wanted to investigate three things: is there a link between marijuana use, prediabetes or the more damaging type 2 diabetes? Is being overweight or obese, based on body mass index (BMI)/weight, a factor to eliminate before the connection between marijuana and diabetes can be made? And given that there are race/gender and sex/race associations with prediabetes and type 2 diabetes, were these playing a part?

The study populations were drawn from the Coronary Artery Risk Development in Young Adults study.

Marijuana users at 65% greater risk for developing prediabetes

After various adjustments had been made, it was found that among participants who said they were currently using marijuana, there was a 65% increase in the odds of having prediabetes, while those who said they were lifetime users of marijuana showed a 49% increase.

There was no direct link found between marijuana use and development of type 2 diabetes.

The authors say "it is unclear how marijuana use could place an individual at increased risk for prediabetes yet not diabetes."

However, they offer various suggestions regarding this, including the potential exclusion of those from the study with higher levels of marijuana use and the possible effect of marijuana on blood sugar control, compared with other traditional diabetes risk factors.

Commenting on their findings, the research team says:

"Marijuana use was associated with the development and prevalence of prediabetes after adjustment. Specifically, occurrence of prediabetes in middle adulthood was significantly elevated for individuals who reported using marijuana in excess of 100 times by young adulthood.

Future studies should look to objectively measure mode and quantity of marijuana use in relation to prospective metabolic health."

In June, Medical News Today reported on a study published in JAMA claiming there is "lack of evidence" to support benefits of medical marijuana.

Written by Jonathan Vernon