Overuse of opioids can lead to hypersensitivity to pain.

Opioids mimic naturally produced endorphins to dull pain.

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.

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

The body produces its own opioids that act on several receptor types throughout the body, triggering the release of dopamine and suppression of noradrenaline, neurotransmitters associated with reward and alertness, respectively.

Synthetic opioids: a historical and clinical review

In the 19th century, researchers began synthesizing and isolating poppy plant alkaloids, leading to the invention of morphine, codeine, heroin, oxycodone, and others. These highly addictive variants eventually gave rise to illicit use and a widespread underground market, laying the foundation for the current opioid crisis.

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.

Opioid prescription rates by states and counties

The origins of the US' ongoing opioid crisis are typically traced to the more than 1 billion prescription pain pills that flooded medicine cabinets between 2005 and 2019. This prescription opioid epidemic resulted in more than 210,000 fatal overdoses and set the stage for the ongoing crisis fueled by heroin and fentanyl.

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).

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.

Opium is a milky liquid substance extracted from unripe poppy plant seeds

It's been used for ages to reduce pain and induce euphoria, both of which are side effects of the plant's alkaloids—nitrogen-based compounds with pronounced physical effects. Isolating and synthesizing derivatives of these naturally occurring chemicals enabled the invention of morphine, heroin, and other opioids.

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.

From prescriptions to street drugs: Opioids trajectory across America

Exclusive data obtained by The Washington Post from the Centers for Disease Control and Prevention shows how individual counties moved through three waves of the opioid crisis, each wave paving the way for the next. Between 2011 and 2017, the drug responsible for the majority of overdose deaths shifted from prescription pills to heroin to fentanyl. Together, oxycodone, hydrocodone, heroin, and fentanyl have been major drivers in declining life expectancy in the US.

The Cincinnati Enquirer's Pulitzer-winning look at the opioid epidemic

Synthetic opioids kill someone in the US every 16 minutes. Communities across the country have been ravaged by deaths, overdoses, jail time, and babies born with drug-related medical problems as opioid abuse became a typical feature of many American towns. This seven-part exposé provides an inside look at the effect in southern Ohio and northern Kentucky.

Why are drug dealers putting fentanyl in everything?

A few grains of fentanyl, a synthetic opioid far more potent than heroin or morphine, are enough to kill a typical adult human. It's made its way into other, less lethal street drugs, where it may be used to increase the highs experienced by unknowing users, increasing their likelihood of addiction and overdose.

Why is fentanyl poisoning street drugs?

A few grains of fentanyl, a synthetic opioid far more potent than heroin or morphine, is enough to kill a typical adult human. It's made its way into other, less lethal street drugs, where it may be used to increase the highs experienced by unknowing users, increasing their likelihood of addiction and overdose. This 39-minute podcast episode is the first half of a two-part series exploring fentanyl's rise.

A workplace back injury and the opioid prescription that followed set one Texas father on the path the Washington Post's video profile calls his rise to fentanyl 'kingpin.'

The story of the Sackler empire behind highly addictive OxyContin

This investigative report examines how the Sackler family built its fortune through Purdue Pharma’s aggressive marketing of OxyContin, a highly addictive painkiller. Through 2017, the drug had generated more than $30B in sales for Purdue Pharma, controlled by the Sacklers.

Opioid epidemic 101: lawsuits and settlements

State and local governments trying to address the opioid epidemic have sued organizations they believe started and supported the crisis. Companies that made, distributed, or contributed to sales of the highly addictive painkillers are expected to pay more than $50B in settlements. These settlements specifically state that at least 85% of settlement funds must be spent on addressing the epidemic, though where exactly the money is going is unclear.

Fentanyl is better at crossing the blood-brain barrier than other opioids

Among opioids, fentanyl is uniquely adept at crossing the blood-brain barrier—the brain's security fence against harmful substances. This enables a lightning-fast high. It ends just as quickly, sometimes within minutes (where a heroin high lasts hours), and still results in the same withdrawal symptoms.

Addiction develops when the pleasure circuits in the brain get overwhelmed

Normal pleasure circuits become overwhelmed by addictive substances, triggering dopamine floods many times stronger than those induced by everyday reward experiences. The understanding of addiction as a brain disease has led to treatments pairing medication and counseling.

Evidence of opium use dates to as early as 5000 BCE

Archaeological evidence shows the use of the poppy plant for its pain-killing properties likely originated in the Mediterranean before making its way to the East and West via trade. It has since inspired two eponymous wars, and highly addictive derivatives of the naturally occurring substance have led to an ongoing overdose crisis.

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.

Learn about the point of the physical and emotional experience of pain, which has three broad categories that help determine treatment approaches.

One person dies from opioids every 7 to 8 minutes

This collection of infographics by the National Institute for Health Care Management helps put the crisis into perspective. The opioid epidemic has had three waves. Opioid-related deaths increasingly involve synthetic versions of the drug class, contributing to 83 percent of all opioid-related deaths in 2020. Use these infographics to learn more about the crisis.

Addictive drugs can cause dopamine levels to become ten times higher than normal.

Morphine, heroin, codeine, and more were derived from opium

Opium reached the US at about the time early colonists were itching for ways to soothe aches and pains. The active ingredient in the substance was isolated in the early 19th century, eventually leading to the manufacture and commercial sale of morphine, heroin, and other opium-based drugs.

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.

Fast, cheap, and deadly: How fentanyl replaced heroin and hooked America

This interactive article details how fentanyl has largely replaced heroin in the drug trade, with fatal results. Fentanyl was first developed in 1959 as an anesthetic for pain relief, but the drug took hold in the US black market in 2014 and has since exploded in the intervening decade.

Learn about the US opioid crisis in this free course

Where did the US opioid crisis come from, and how did it spread? Learn this and more in this free, online Harvard University course. Learn about the disease model of addiction treatment and management, and get up-to-date with public health and law enforcement's current harm reduction practices. This free resource gives users a greater understanding of opioid addiction and the epidemic still haunting the US.

Opium's history traces from religious use to mass-market commercial products

Religious or medical use of opium was present across Europe and Asia as early as 5000 BCE. By the 16th century, humanity had come to see opium as more than medicine: It was a marketable product. This perspective also defines today's relationship with opioids, highly addictive painkillers at the heart of an ongoing drug crisis.

Narcan is an opioid antagonist that can rapidly reverse overdoses

Naloxone, also known by the brand name Narcan, is an opioid-overdose reversal medication that typically begins working within a few minutes. An opioid antagonist, the treatment attaches to opioid receptors without activating them, forcing opioid molecules out of their respective receptors and allowing users' breathing rates to normalize.

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.

See how DOJ prosecutors took down a pharmaceutical company's executives over the opioid crisis

This FRONTLINE documentary follows federal prosecutors as they used anti-racketeering laws to convict executives at Insys Therapeutics, a pharmaceutical company that bribed doctors to overprescribe a fentanyl painkiller.

Your favorite music can minimize physical pain, according to a 2025 study on how music can bring solace and address pain.

If hearing is damaged, the brain may amplify remaining sounds, perhaps causing tinnitus.

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.

Researchers have investigated the benefits of extreme pain rituals, exploring how and why we engage in these events when humans generally naturally avoid pain and perceive it as a negative experience.

Skull bone marrow may be playing a key role in chronic pain.

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.

Explore the biology of pain and why the experience of pain may differ widely from one person to another.

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.

The subjectivity of pain means that one person's kidney stones may be another's childbirth, but most sources of pain do have objective, underlying causes.

Theories vary on why we love to eat spicy food—even when it hurts.

Drugs 101: An interactive guide

What's the difference between opioids and psychedelics? This guide details specific drugs and their various associated effects. Drugs in this wheel fall into seven categories: stimulants, depressants, empathogens, psychedelics, dissociatives, cannabinoids, and opioids.

High-powered red light therapy—delivered directly to nerve fibers via a fiber optic needle—has been used in recent experimental research to suppress pain.

Over 28% of US adults use yoga for pain management.

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.

Fame can trigger addictive, drug-like highs in the brain

Differences in the type of fame, such as movie stardom, sports, and internet virality, can produce varying degrees of dependence on individuals based on their age and background. Some individuals—particularly children—can develop drug-seeking behavior as they pursue continuous dopamine spikes if they lack an existing sense of fulfillment from elsewhere.

A major dopamine hit from social media use comes from unpredictability—not knowing if the content users post or share will get the 'like' from other users, triggering cycles of anticipation similar to those experienced with a slot machine.

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.