Released when the body encounters stress or pain, endorphins are a natural brain chemical that can provide a “rush” of pleasure similar to that experienced with opioid drug use. Endorphin rushes are often reported by athletes after long, intense exercise sessions or in the wake of a physical injury.

The discovery of endorphins dates to the 1970s, when researchers were puzzled to discover that the brain had a special set of receptors that responded to opiate drugs like morphine. They thought it was odd that brains from all over the world were equipped to deal with a drug originally found only in the Middle East. The existence of the receptors provided a clue that the body manufactured its own natural painkillers. These chemicals, sometimes known as endogenous opioids, were soon discovered in the body.

Unlike opioids, the body’s natural endorphins are not addicting—at least not physically. The chemicals are short-lived and disappear before the body can develop any form of dependency on them. Additionally, people feel no withdrawal symptoms when endorphins aren’t produced.

Some people claim to be addicted to endorphins, however, in the form of a “runner’s high” achieved during prolonged, intense running. The idea of runner’s high had been hypothesized for years, but because it wasn’t possible to look inside someone’s brain before and after exercise, it remained unproven until 2008. German researchers used positron emission tomography (PET) scans combined with psychological mood tests to prove that running did indeed provide a flood of endorphins to the limbic and prefrontal areas of the brain—the parts associated with emotion and euphoria. It’s believed that endorphins are released into the blood when oxygen flow to the muscles decreases and lactic acid accumulates in a process called acidosis, which may cause cramps and physical exhaustion.

ADDITIONAL FACTS

  1. Studies have shown that people who experience chronic pain have lower-than-normal levels of endorphins in their spinal fluid. Some medications and procedures, such as acupuncture, may activate endorphin systems in these patients.
  2. Endorphins also stimulate the immune system by activating natural killer cells in the blood and can postpone the effects of aging.
  3. There are four different types of endorphins: alpha, beta, gamma, and sigma. Beta-endorphins consist of 30 amino acid subunits and show the greatest increase during exercise.