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For years, some studies have found scary evidence that metformin may raise your risk of memory and thinking problems. But other research suggests the drug may help prevent or even reverse such difficulties. Who’s right?

A large new study may change what you think about this common diabetes medicine.

Behind the controversy

Millions of people with type 2 diabetes take metformin every day—and no wonder. It’s a cheap, reliable way to help lower blood sugar when diet and exercise don’t do enough. Metformin is also frequently prescribed to help individuals with prediabetes reduce their risk of developing type 2 diabetes.

People with type 2 diabetes have an increased risk of dementia and other cognitive disorders. Because so many of them use metformin, researchers have long wondered whether the drug might be to blame. But one study after another has produced conflicting results.

Seeking better answers

Some of those studies had shortcomings: they were too small, too brief, or not well constructed enough to prove their point. To help settle the issue, researchers at Columbia University Medical Center rigorously analyzed data on more than 2,000 adults who were followed for over eight years.

Their conclusion: metformin has no effect, good or bad, on cognition.

Though the study was conducted on people with prediabetes, researchers believe the findings should also reassure individuals with type 2 diabetes who may have worried about metformin’s safety. But the study might disappoint those who hoped the drug could protect them from mental decline.

This latest word on the subject will probably not be the last word. Researchers are usually the first to say that additional studies are needed to confirm new findings.

If you notice possible signs of memory or thinking problems, talk them over with your doctor. He or she can help you know whether what you’re experiencing is normal and harmless or may need professional attention.

Have you noticed any possible side effects of metformin? Tell us what you’ve experienced by adding a comment below.