Current and former marijuana users are more likely to have prediabetes, a state of poor blood sugar control that puts them at risk for diabetes, a new study finds.

Marijuana is the most frequently used illicit drug in America with an estimated 19 million users, a prevalence that is expected to grow as laws prohibiting it become more relaxed.

Despite the growing trend to legalize it, little is known about its effect on metabolic health. Some studies suggest pot can reduce the risk of diabetes, while others find the drug is associated with overeating, which can contribute to the disease.

In this new study, University of Minnesota School of Public Health researchers investigated the association with self-reported marijuana use and current prediabetes and full-blown diabetes in individuals enrolled in a study with a 30-year database.

They found that current users of marijuana had a 65 percent increased risk of having prediabetes and a 49 percent if they had used it 100 times over their lives, compared to people who were never users. This association was unrelated to either body mass index (BMI) or waist circumference.

But no link between marijuana use and full-blown diabetes was discovered, even in participants tracked over an 18-year follow-up period, the researchers said.

The study was published in the journal Diabetologia.