What are endorphins?

female runner taking a break
Runners often experience a rush of endorphins, also called a "runner's high." Halfpoint Image/Getty Images

It's not uncommon to hear someone talk about getting an "endorphin rush." Sex, exercise, even hot peppers -- all sorts of things are credited for these euphoric highs. So what are endorphins, and are they really responsible for our feelings of excitement or satisfaction?

In the early 1970s, researchers were studying how the brain is affected by opiates, such as heroin or morphine. They found that opiates interact with specialized receptors in cells that are primarily massed in the brain and spinal cord. When opiates enter these receptors, they hinder or block the cell's transmission of pain signals. But why, wondered the scientists studying this phenomenon, would these specialized receptors exist in the first place? The most plausible answer was that opioid receptors exist due to the presence of an opiatelike substance produced naturally in the body.


Enter endorphins: your own private narcotic. Endorphins are neurotransmitters, chemicals that pass along signals from one neuron to the next. Neurotransmitters play a key role in the function of the central nervous system and can either prompt or suppress the further signaling of nearby neurons.

Endorphins are produced as a response to certain stimuli, especially stress, fear or pain. They originate in various parts of your body -- the pituitary gland, your spinal cord and throughout other parts of your brain and nervous system -- and interact mainly with receptors in cells found in regions of the brain responsible for blocking pain and controlling emotion.

Until recently, much of what we've learned about endorphins has been gained from monitoring endorphins in the human bloodstream and in rats' brains. It wasn't possible to measure endorphin levels in the human brain without harming the subject, so the role of endorphins in the "runner's high" and other periods of euphoria or mood change were still hotly debated. However, new imaging methods allow researchers to study the ebb and flow of endorphins as they interact with human brain cells, verifying their role in the rush that exercise -- and other triggers -- sometimes prompts.

There are at least 20 different kinds of endorphins, and one kind, beta-endorphins, are stronger than morphine and have been shown to play a part in everything from alcoholism to diabetes to aging of the brain [source: Dalayeun].

Next, we'll learn how endorphins can make us more emotional than an hour spent standing at the craps table.


Endorphins and Emotions

happy girl with arms spread
The body's own opiate can give you a feeling of euphoria.

Endorphins block pain, but they're also responsible for our feelings of pleasure. It's widely believed that these feelings of pleasure exist to let us know when we've had enough of a good thing -- like food, sex or even companionship -- and also to encourage us to go after that good thing in order to feel the associated pleasure.

The majority of your emotions (and memories) are processed by your brain's limbic system, which includes the hypothalamus, the region that handles a range of functions from breathing and sexual satisfaction to hunger and emotional response. The limbic system is also rich with opioid receptors. When endorphins reach the opioid receptors of the highly emotional limbic system, and -- if everything is working normally -- you experience pleasure and a sense of satisfaction.


Intriguingly, endorphins (or a lack thereof) may be responsible for certain forms of mental illness such as obsessive-compulsive disorder. When you, the average person, are washing your hands, there's a point when you register that the task has been satisfactorily completed. If endorphins are at least partly responsible for saying "when," a person who doesn't have enough may never receive the mental cue to stop washing his or her hands and will continue until that signal is received.

It's been theorized that problems with endorphin production or the binding process may be responsible for clinical depression or sudden shifts in emotions. Some people who engage in self-hurting behaviors may do so in part to feel the feelings of euphoria and emotional isolation that can -- for them -- be prompted by controlled amounts of self-inflicted pain.

Endorphins may also be responsible for heightened states of rage or anxiety. If your endorphins overdo their job or the hypothalamus misreads the endorphin cue, you could be flooded with "fight-or-flight" hormones at the slightest hint of trouble or worry.

Endorphins affect us like codeine or morphine do, but without the addiction. Regular users of opiates generally aren't models of emotional stability, and steady, controlled endorphin release is something of a pipe dream. Making matters worse, some of us have brains that act like ambitious drug dealers, and others of us only dabble now and then. This variation can help explain why one person reacts differently from another to the same stimulus.

Endorphins have a leg up on opiates, however. Endorphins may be responsible for the "placebo effect," owing to the real response of endorphin-release prompted by a tricked hypothalamus, creating a sense of well-being after consuming a much-hyped sugar pill, or even after simply anticipating something pleasurable.


Endorphin Triggers

What gives one person an endorphin rush might be a total dud for someone else.

Many things can trigger the release of endorphins. Though many triggers are known to exist (which we'll discuss in a moment), the primary triggers are stress and pain. When your hypothalamus detects pain, it issues several orders, one of them being, "Quit telling me it hurts!" (Another one? "Quit touching the hot stove!")

The hypothalamus is the command-and-control center of your endocrine system. It decides when you need to eat, when you should begin puberty and when you need a big dose of endorphins, among many other functions. It keeps tabs on every part of your central nervous system, and hormones are released to other parts of the body when the hypothalamus wants to make an adjustment.


When this part of the brain calls for endorphins, it initiates a chain of messages by chemically prompting the pituitary gland to release its own chemicals that then make their way to glands throughout your body and on down the line until endorphin-containing neurons release them. These endorphins then find their way to the brain's opioid receptors.

Endorphins are produced throughout your body and requested by the hypothalamus, but what else besides stress and pain triggers the release of endorphins?

  • Exercise -- The "runner's high" really exists, but you'll need to work for it. Heavy weightlifting or intense aerobic activity that includes periods of sprinting or increased exertion will trigger the greatest response.
  • Meditation or controlled-breathing exercises -- Tai chi, Pilates and yoga are believed to trigger endorphins.
  • Childbirth -- Giving birth to a child is clearly a subcategory of both pain and stress.
  • Alcohol -- Light to moderate drinking stimulates endorphins, but heavy drinking doesn't. Drugs that block the attachment of endorphins to receptors have been shown to eliminate cravings in alcoholics.
  • Chili peppers -- Capsaicin, which puts the burn in chilies, also triggers the body to release some fire-quenching endorphins.
  • Bodywork -- Both acupuncture and massage therapy trigger your inner drug dealer.
  • Ultraviolet light -- This may explain why some users of tanning beds achieve something of a "runner's high," and why others may overuse them at the risk of their health [source: Wake Forest University Baptist Medical Center].

Want more on exercise and happiness? Try the articles on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Dalayeun, JF; et al. "Physiology of beta-endorphins. A close-up view and a review of the literature." Biomedicine & Pharmacotherapy. 1993, Vol. 47, issue 8.http://www.ncbi.nlm.nih.gov/pubmed/7520295
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  • Sailing, Jasmine. "Endorphins: Free Smack!" Morbid Curiosity, 1998. http://cyberpsychos.netonecom.net/jsailing/actual/heroin.html
  • Stoppler, Melissa Conrad, MD. "Endorphins: Natural Pain and Stress Fighters." March 15, 2007. (June 1, 2009)http://www.medicinenet.com/script/main/art.asp?articlekey=55001
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  • The Merck Manuals Online Medical Library. "Principles of Endocrinology." Nov. 2005. (June 1, 2009)http://www.merck.com/mmpe/sec12/ch150/ch150a.html
  • University of Bonn. "Runners' High Demonstrated: Brain Imaging Shows Release Of Endorphins In Brain." ScienceDaily. Mar. 6, 2008. (June 5, 2009)http://www.sciencedaily.com­/releases/2008/03/080303101110.htm
  • Wake Forest University Baptist Medical Center. "Small Study Points To Addictive Effects Of Frequent Tanning." ScienceDaily. Mar. 29, 2006.http://www.sciencedaily.com­/releases/2006/03/060329084053.htm
  • WebMD. "Meditation Boosts Mood, Immune System." Aug. 18, 2003. (June 4, 2009) http://www.webmd.com/balance/news/20030818/meditation-boosts-mood-immune-system
  • Zimmerberg, Betty. "Synaptic Transmission: A Four Step Process." Multimedia Neuroscience Education Project, Williams College Neuroscience. 1998. (June 5, 2009) http://www.williams.edu/imput/introduction_main.html