As evidence has mounted that new diabetes and weight loss drugs can provide a variety of health benefits, the FDA has approved Novo Nordisk’s semaglutide for heart disease and Eli Lilly’s tirzepatide for sleep apnea.

Now, as the companies run trials to flesh out the potential of the drugs to treat other conditions, an observational study from Washington University in St. Louis has shed more light on the benefits—as well as the risks—of using the metabolism-altering treatments.

According to the study, which was published Monday in Nature Medicine, researchers found that use of the new medicines may reduce the risk of Alzheimer’s disease and substance abuse disorders while increasing the risk of digestive issues and arthritis.

In researching 175 health categories, the scientists catalogued 42 possible benefits linked to use of the drugs and 19 ways that they may cause damage.

The study is based on health records from the U.S. Department of Veterans Affairs and includes 215,970 diabetes patients taking the new drugs. For comparison, the researchers reviewed data on 2.4 million patients who use other types of diabetes treatments. 

It is the largest study ever of the drug category—which includes Novo Nordisk’s GLP-1 treatments Ozempic and Wegovy and Eli Lilly’s dual-action GLP-1/GIP agonists Mounjaro and Zepbound.

“We’re saying there are beneficial effects, but we’re also saying they’re not without risks,” Ziyad Al-Aly, M.D., the leader of the study and a clinical epidemiologist and researcher at Washington University, said in a press conference last week.

Al-Aly and his research group have gained notoriety with their findings on long COVID and for establishing links between air pollution and diabetes and between proton pump inhibitors and heart and kidney diseases.

As for Alzheimer’s and other neurocognitive disorders, the research showed that use of the new diabetes and obesity drugs reduced the risk by 12%, but Al-Aly said the figure is likely larger because the study spans just 3.5 years and Alzheimer’s symptoms develop over a much larger time span.

The study also linked use of the drugs to a reduction in the use of alcohol, opioids, tobacco and marijuana. They also helped cut the risk of schizophrenia episodes and seizures. 

Among the other benefits observed were with reductions in heart attacks, stroke, blood clotting, liver cancer, kidney disease, bacterial infections, pneumonia and Parkinson’s disease, according to the researchers.

On the flip side, researchers found use of the diabetes and weight loss drugs increased the risk of joint pain, inflammation in the pancreas, low blood pressure, fainting, headaches, kidney stones and a variety of other digestive issues that have been well documented including nausea, stomach inflammation, diverticulitis and hemorrhoids.

“Our goal here was to literally map the landscape by association or create an atlas of associations,” Al-Aly said. “We will be doing more studies that focus on individual diseases with several controls as well as looking at absolute risk reduction in different populations, in different subgroups as well.”

Al-Aly also pointed out seemingly conflicting evidence in the study, including an increased risk of developing kidney stones along with a decreased risk of developing kidney disease.