The new study, published in Nature Health, covers more than half a decade of posts from nearly 70,000 Reddit users and highlights two main classes of symptoms that warrant further study: reproductive symptoms, including irregular menstrual cycles, and temperature-related complaints, such as chills and hot flashes.

"Some of the side effects we found, like nausea, are well known, and that shows that the method is picking up a real signal," says Sharath Chandra Guntuku, Research Associate Professor in Computer and Information Science (CIS) at Penn Engineering and the study's senior author.

"The underreported symptoms are leads that came from patients themselves, unprompted, and clinicians could potentially pay attention to them."

"Clinical trials generally identify the most dangerous side effects of drugs," adds Lyle Ungar, Professor in CIS and a co-author on the study. "But they can fail to find what symptoms patients are most concerned about; even though social media is not necessarily representative, a large collection of posts may reflect additional concerns."

The researchers caution that their findings are not causal. "We can't say that GLP-1s are actually causing these symptoms," notes Neil Sehgal, the study's first author and a doctoral student in CIS advised by Guntuku and Ungar.