Marijuana users may face future risks of developing prediabetes — elevated levels of blood sugar that can be a precursor to full type 2 diabetes, according to a new study.

Current users and those who have used marijuana earlier in life are more likely to have or develop prediabetes than people who have never used it, the researchers say.

A survey of more than 3,000 people in the U.S. found that current adult users of marijuana were 65 percent more likely to exhibit poor blood sugar control, while those who have given up marijuana but used it at least 100 times in their lives showed a 49 percent greater chance of developing prediabetes, the researchers wrote in Diabetologia, the journal of the European Association for the Study of Diabetes.

The new findings are in contrast to some earlier studies on associations between marijuana and health, which yielded contradictory results in terms of diabetes.

Some previous work had suggested that marijuana use could reduce the risk of developing diabetes — something not borne out in the new research.

"These results contrast with those previously reported on marijuana use and metabolic health," said study leader Mike
Bancks of the University of Minnesota School of Public Health. "Future studies should look to objectively measure mode and quantity of marijuana use in relation to prospective metabolic health."

Diabetes is classified as a metabolic condition.

While the study revealed an association between marijuana use and prediabetes, it did not find a definite link to an increased risk of type 2 diabetes, the researchers took pains to point out.

That's something that should get further analysis, they wrote in their published study.

"It's unclear how marijuana use could place an individual at increased risk for prediabetes, yet not diabetes," Bancks acknowledged.

In some of the earlier studies examining possible links between marijuana and risks of diabetes, it had been unclear whether people were using the drug before they developed diabetes, or afterward, he said.

"There are many questions about the health effects of marijuana use where the answers are unknown," he added. "The increased legalization and use of marijuana will draw more attention from researchers and users, and we will learn more as research on the health effects of marijuana use increases."