Overuse of opioids can lead to hypersensitivity to pain

Opioids mimic naturally produced endorphins to dull pain

Once in the body, opioids bind to naturally occurring opioid receptors typically used by endorphins to temper pain. They trigger the release of dopamine, a desire-related hormone, and decrease noradrenaline, a neurotransmitter involved in heart and breathing rate regulation, meaning high doses can slow these processes to dangerous levels.

How the body produces its own opioids

Opioids act on the body's own opioid receptor system. The endogenous opioid system comprises four molecule receptor types found throughout the body. When activated, these receptor types trigger the release of dopamine and suppression of noradrenaline, neurotransmitters, respectively, associated with reward and alertness. This opioid system helps regulate emotions, and its disruption is linked to neuropsychiatric conditions, including depression, PTSD, and Alzheimer's disease.

Opioids are a class of drugs including fentanyl, heroin, oxycodone, and more

Since the dawn of pain, living things have sought ways to mitigate this evolutionary warning signal. One of nature's most effective painkillers is opium, a highly addictive, milky latex extracted from poppy plants. This forms the basis of one of the most prescribed classes of modern drugs.

Why the human brain loves opioids

When opioids enter the brain, they dock in receptors, blocking electrical pulses such as those that communicate pain. They also trigger the release of dopamine, a neurotransmitter tied to motivation and associated with stress relief.

The three waves of the opioid crisis: overprescription, heroin, and fentanyl

The US opioid crisis has unfurled in three distinct waves, each spiraling into an epidemic that's killed millions. The first crested in the 1990s with the overprescription of opioids for pain relief. The second manifested as heroin overdoses in the 2010s. The third began in 2013 with the rise of deaths related to tramadol and fentanyl.

Methadone binds to the same receptors as heroin and other opioids

Methadone is a long-acting opioid agonist that works by binding to the same brain receptors as other opioids (like heroin or morphine), but without producing intense euphoria. It reduces withdrawal symptoms and cravings, helping people stabilize and avoid illicit opioid use.

Fentanyl can be up to 100 times more potent than morphine

A synthetic opioid, fentanyl is highly addictive and incredibly fast-acting—a fatal dose is equal to a few grains of table salt. Once it enters the body, fentanyl floods naturally occurring opioid receptors, which can cause the body to shut down its breathing reflex, leading to a fatal overdose.

Drug tolerance and withdrawals are consequences of overloading dopamine circuits

Addictive substances or behaviors will typically flood our brains with more dopamine than usual. In response to the overstimulation, our brains will decrease the number of available dopamine receptors. This results in the need for more stimulus for the same response (tolerance) and a rise in negative feelings when the stimulus is absent (withdrawal).

Overuse of antibiotics gives bacteria more opportunity to evolve their defenses

The overuse and misuse of antibiotics are significant contributors to the rise of antibiotic resistant bacteria. Experts say antibiotics should only be used for specific medical problems, and patients need to be sure to take antibiotics exactly as prescribed in order to reduce the risk of antibiotic resistance.

Naltrexone blocks the reward effects of alcohol and opioids

Naltrexone is used to treat alcohol and opioid dependence, blocking opioid receptors in the brain, reducing cravings, and preventing the euphoric effects of alcohol or opioids. It is nonaddictive and works best as part of a comprehensive treatment plan, including counseling or therapy, to support long-term recovery.

Itching is caused by stimulated nerve cells in the skin

Scratching produces low-level pain signals to the brain, distracting from the itch. Scratching also releases serotonin, a neurotransmitter that creates a happy sensation, which resets the itch signal. This can cause a cyclical itch-scratch cycle.

Over time, people develop a resistance to spicy foods

TRPV1 is a receptor in the body that detects potentially harmful things and responds in a variety of ways, including sweating, tearing up or a runny nose. Over time, more exposure to spicy foods can build up a resistance that minimizes these reactions.

When common sounds become disturbing

Misophonia causes certain sounds to feel violating, triggering a "very visceral kind of experience" filled with extremely unpleasant emotions, including annoyance, anger, and disgust. A 2017 study found that people with misophonia have elevated activity in the brain's anterior insula—a region associated with interoception, emotional processing, and behavioral responses—when exposed to trigger sounds. Ongoing research suggests trigger sound context affects the severity and manifestation of the condition.

Hereditary hyperosmia is the official term for being a super-smeller

Some sniffers with this rare trait may be more sensitive to pleasant smells, while others may be more attuned to unpleasant scents. Some research suggests that certain genetic mutations are associated with a heightened sense of smell.

Chronic inflammation can cause cellular damage and could lead to cancer

Over time, this cellular defense system can inadvertently damage cells and tissues when it's in this heightened alarm mode over a prolonged period. This occurs because, when immune cells are sent somewhere without a true target, they may attack healthy cells and tissues.

The word allergy is partly derived from the Greek word 'allos' for 'other'

For people with allergies, their immune systems recognize substances as a harmful "other"—cuing an inflammatory response. This podcast explores allergy details and related topics, including how scientists are interested in if the same allergic response mechanisms could underpin other health issues, including severe, painful symptoms around the time of menstrual cycles. Since estrogen acts on white blood cells called mast cells, which leads to the release of histamines—similar to what happens during allergic responses—an understudied question is whether the same process is fueling some of the uncomfortable symptoms around menstruation. An allergist guest notes this raises questions about if antihistamine medications like Pepsid might alleviate them, something that hasn't yet been explored in clinical trials.

Over 28% of US adults use yoga for pain management

According to a 2022 study, 28.8% of adults used yoga as a way to manage pain. That's a significant uptick from 2002, when only 11.2% did. The most used approach was chiropractic, which 85.7% used.

Doctors ignored women's pain as a nurse replaced their fentanyl with saline

This five-part podcast series, produced by Serial Productions, focuses on the experiences of women undergoing fertility treatments at a Yale clinic where a nurse secretly replaced pain medication with saline solution. This led to women experiencing excruciating pain during procedures, but the clinic downplayed or ignored their complaints.

Nerve axons become damaged by leprosy, so patients may lose feeling in their skin

Infection of the peripheral nerves—nerves outside the brain and spinal cord—is a known complication of leprosy. That damage can cause patients to lose their sense of touch and the ability to feel pain or temperature in affected areas, leading to accidental injury.

Would you opt for a life with no pain?

Philosopher Robert Nozick famously posed a question challenging the philosophy of hedonism—the idea that maximizing pleasure is the greatest good in life. His thought experiment imagined people could plug into a machine that would give total pleasure, suggesting the idea itself is not a compelling or desirable one. Learn the arguments and ideas in this short video.

Key symptoms of burnout can be both mental and physical

Burnout can be accompanied by several symptoms, including low energy and chronic fatigue, trouble concentrating, difficulty sleeping, and depression. It may even manifest physically as musculoskeletal pain, headaches, stomach and intestinal pain, and more. More intense cases have been linked to cardiovascular and mental health disorders.

Can you microdose GLP-1 agonists like Ozempic?

GLP-1 agonists like Ozempic can help with weight loss, diabetes, and anti-inflammation. For some users, normal doses are too much. So, they've started "microdosing"—taking a smaller amount than the lowest increment of the drug available. While not yet backed by clinical trials, some doctors observed positive effects for certain people.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for years

The substance can still cause rashes even after being on shoelaces, clothing, sleeping bags, boots, or other clothing for multiple years—some reports say five years on surfaces—so they all need to be washed after outdoor adventures with the plants.

'Genericide:' Learn how too much brand awareness can hurt a company's trademark

When a brand becomes so popular that consumers regularly call the product by the brand name like a noun or verb, that trademark becomes generic because consumers no longer associate a specific brand with a certain product. A generic product can hurt a company's right to trademark or even cause companies to lose it. (Some users may experience a paywall.)

AI hallucinations are inaccuracies or falsehoods in generated content

AI hallucinations are a by-product of the sequential creation of content based on patterns in text, which may not reflect the context or meaning behind a prompt. Back-end issues like biased datasets and overfitting of model data contribute to hallucinations.

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

Telehealth demand for GLP-1s for weight loss is booming as consumers seek easier access.

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

11 people died from firework injuries in the US in 2024.

Watch how algorithms can be designed to train themselves and self-improve without human input, to the point where the optimized code is too complex for programmers to understand.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

Cultural norms about how to handle the bodies of loved ones in communities in West Africa have hampered Ebola responses.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

After her fellow cult members tried to kill her with an LSD-infused hamburger, one member of the Manson Family, the murderous cult led by Charles Manson, decided to testify against the group's leader.

The power and influence of the American presidency have expanded significantly over time—far beyond what the founders envisioned.

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.