Running is good for your health in more ways than one. Research has shown that in addition to improving your physical health, running can also have a positive impact on the quality of your emotional and mental health. Many people tout the mental health benefits afforded by running, such as reducing stress and making you feel accomplished, but there has been much debate over whether there is actually such a thing as a “runner’s high.”

When running or participating in other forms of prolonged exercise, some people experience a feeling of euphoria, often accompanied by reduced anxiety and less pain. This is what runners refer to as a runner’s high. For many years, people believed that the release of endorphins while running was responsible for these feelings, but that may not be the whole story.

Sure, endorphins are released when you run and these may trigger a positive feeling in your body and reduce your perception of pain. Endorphins are produced in the brain’s hypothalamus and pituitary gland when your body is under physical stress or experiences pain. These neurochemicals are similar in structure to the drug morphine and work in a comparable fashion, activating opioid receptors in the brain to help minimize discomfort.

But are endorphins the sole reason you get a runner’s high? Probably not. Although numerous studies have shown that endorphin levels rise in the blood when running, the research doesn’t prove that endorphin levels in the brain also increase. It is the endorphins in your brain, not in your blood, that would cause that euphoric state many equate with achieving a runner’s high.

Researchers in a German study found that endorphins can’t pass through the blood-brain barrier. They did find, however, that a lipid-soluble endocannabinoid called anandamide can travel from the blood to the brain, unlike endorphins. Their findings indicate that endocannabinoids may actually be what plays a role in that sense of well-being runners feel. The researchers tested the effect of endocannabinoids on mice running on an exercise wheel and their results suggest that endocannabinoids may play a part in reducing anxiety and increasing pain tolerance, two key aspects of a runner’s high. Other aspects of a runner’s high, such as a feeling of euphoria, are too subjective to study in mice.

Although the science behind what actually causes a runner’s high can be confusing, it doesn’t mean that achieving a runner’s high isn’t possible. That sense of euphoria and well-being some runners feel is very real, albeit subjective. No matter what is going on within your body to actually make it happen, experiencing the feel-good effects of a solid run is just another reason to lace up your sneakers and get moving.