Tylenol (acetaminophen), the popular over the counter pain reliever, seems to have a previously unknown side effect: dulling your positive feelings.

"Rather than just being a pain reliever, acetaminophen can be seen as an all-purpose emotion reliever," says Geoffrey Durso, author of a new study conducted at Ohio State University. About 80 college students were given acetaminophen, then were shown emotional images. The photos included extremely unpleasant images, such as crying, malnourished children; neutral images, like a cow in a field; or pleasant images like young children playing with kittens. Those given acetaminophen had significantly blunted emotional reactions.

Acetaminophen doesn’t behave like many other common over the counter pain relievers, such as ibuprofen or aspirin. Once inside the body, acetaminophen is metabolized to AM404, an endogenous cannabinoid reuptake inhibitor, working its effects similarly to how cannabis works its painkilling power.

Researchers don’t know if other pain relievers like ibuprofen or aspirin also blunt emotions, although they plan on studying that possibility.