Why the human brain loves opioids

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.

Overuse of opioids can lead to hypersensitivity to pain

Opioid misuse can lead opioid-induced hyperalgesia, where the body becomes increasingly sensitive to pain. The body produces its own opioids as a way to temporarily block pain signals. When met with external opioid use, the body ratchets up pain sensitivity to ensure it senses the pain necessary to trigger its own response.

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.

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.

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

Now recognized as a physiological brain disease, addiction rewires the brain's reward system to make drugs feel necessary and weaken self-control by dulling the relative effects of natural rewards like food and social connection.

How can octopuses and MDMA help scientists understand the human brain?

Research shows that psychedelics may induce something called "critical periods" in the adult brain, which can make our brains more open to learning and changing, like they once were back in early childhood. Psychedelics similarly change how social creatures like octopuses behave, which demonstrates that these animals could help us better understand our own neurobiology.

Love and heartbreak trigger powerful, neurochemical-driven changes in the body

The feeling of falling in love floods the brain with dopamine, oxytocin and serotonin, which collectively dull pain and boost immunity. However, the loss of these chemicals during a break-up produces withdrawal-like symptoms and heart issues, such as high blood pressure.

Grief rewires the human brain

The human brain handles stress and emotional traumas similarly. In response to the emotional stress of a situation like the death of a loved one, divorce, or abuse, the brain may strengthen or weaken connections between nerves to form new neural connections. Over time, chronic stress can diminish brainpower, reducing overall nerve growth and memory to shift resources to enable elevated fear responses and enable humans to survive.

'Susan's Brain': what happens to the brain during addiction

This engaging animation from Harvard Online breaks down the neuroscience of addiction through the story of “Susan’s brain,” demonstrating how addictive substances hijack normal reward pathways. Through clear visual metaphors and approachable narration, it explains complex brain chemistry in understandable terms.

This is the human brain on the world's strongest psychedelic

Within seconds of inhaling a high dose of vaporized synthetic 5-MeO-DMT—a lab-produced substance that otherwise is naturally derived from the glands of the Colorado River toad—it induced slow brain waves. Such waves are typically associated with unconsciousness due to a coma or anesthesia, perhaps explaining why users describe feeling like everything falls away. The compound is currently in clinical trials for treating depression.

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.

Why we pay to be scared

Why do we love roller coasters? It’s not just the speed or height, it’s controlled fear. Your brain thinks you’re in danger, then rewards you with dopamine.

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.

The reason some people love exercise may be because of their microbiome

Certain gut microbes in mice trigger dopamine release and drive motivation to exercise more. Scientists are investigating whether humans carry similar microbial patterns that influence our natural inclination towards movement, exploring how unseen microbial ecosystems may shape mammalian fitness behavior and reinforce innate reward pathways. (Some users may experience a paywall.)

Your favorite music can minimize physical pain

According to a 2025 study, a person's favorite music can help them address pain. The report stated that “listening to a favored music genre has a significant positive influence on pain tolerance, irrespective of the kind of genre.”

The limbic system drives emotion, memory, and survival instincts in the brain.

This interconnected group of brain structures—including the amygdala, hippocampus, thalamus, and hypothalamus—processes emotional responses, regulates bodily functions, and plays a key role in memory and learning.

Trauma is a primary risk factor for substance use disorder later in life

Studies indicate 75% of people with substance use disorder have experienced at least one traumatic experience in their life. These experiences alter brain function, leading to heightened stress and emotional pain. Substances offer temporary relief, but this often results in dependency.

Humans are wired to pick up on each other's emotion, making laughter contagious

The reaction plays a key role in establishing interpersonal connections and relieving stress by releasing endorphins—feel-good hormones. A 2021 study identified at least 65 animal species that produce playful sounds, such as laughter.

What is the brain up to when the mind wanders?

As you stare into the distance while washing your home's seemingly never-ending pile of dishes, the brain activates its default mode network. This collection of "task-negative" brain regions associated with memory, reward, action consideration, and prediction alight with activity when humans mentally turn inward, possibly giving rise to the brain's ability to wander and humans' ability to construct internal narratives about the world.

Neural rhythms shape how we move, focus, remember, and interact with the world

Millions of neurons in the brain produce rhythmic electrical signals, or brain waves, that guide physical movement and help form and store memories. Researchers also use these rhythms to create brain-computer interfaces, letting people control devices using only their thoughts.

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.

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

Learn about the neuroscience and psychology of why we crave comfort foods

The term was coined in 1966, when psychologist Joyce Brothers suggested humans turn to food associated with the feelings of comfort from their childhoods when experiencing emotional distress. Since then, studies have shown that the familiarity, reliability, and convenience of certain foods from one's upbringing can become tied to feelings of nostalgia.

Why patterns in art are so pleasing

Repeated visual cues like shapes or lines derive from the brain's innate compulsion to identify faces, places, bodies, and more. With repeated shapes, the brain seeks out resolution to the subtle variations between them. See examples in art and music.

What happens to the brain during migraine?

Migraine is a neurological condition that can cause debilitating symptoms across various bodily functions. So, what exactly is happening in the brain during these attacks? This five-minute video briefly overviews the internal machinations behind the painful episodes. An incapacitating headache is a common symptom of migraine, though migraine can occur without any headache.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

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

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

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

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

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

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

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

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.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

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.

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

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

US consumers collectively owe more than $1T to credit card companies—almost as much as they owe in auto loans.

A vending machine run with Anthropic's AI went out of business after it was convinced to give away items for free and sell a video game console.

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.

Graffiti dates back to at least ancient Pompeii, where citizens scrawled messages to one another on public walls

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks

Domino's Pizza's 30-minute delivery guarantee was responsible for the chain's 1980s surge, but it was discontinued after the company was found liable for delivery driver accidents.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

A Yale student wrote a profound essay about the consulting industry's influence on elite college students that was published in a book of her writing after she died in a post-graduation car accident.