Why the human brain loves opioids

Opioids mimic naturally produced endorphins to dull pain.

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.

Overuse of opioids can lead to hypersensitivity to pain.

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

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.

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.

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.

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.

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.

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).

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.

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.

Chronic drug use can cause neurological changes in the brain

Neuroscientist Judy Grisel breaks down the biology of addiction, examining how drugs hijack the brain’s natural reward system and create lasting neural changes. The physiological and neurological impacts of chronic drug use require a multifaceted treatment approach.

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.

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

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.

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.)

What exactly is dopamine?

Dopamine is a neurotransmitter—a chemical released by neurons that enables neural communication—that makes people want things with an "almost animalistic desire," compelling them to snack or check phone notifications. Often misrepresented as a "pleasure" chemical, dopamine is involved in motivation, learning, attention, habit formation, and more. Trends like dopamine fasting overinflate its role in mental health and often use it as part of "straw man" biohacking claims.

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.

Some people may be genetically predisposed to loving roller coasters

Recent studies indicate that individuals with higher levels of dopamine may be more prone to thrill-seeking behaviours like riding roller coasters or even doing drugs or shoplifting.

Can the gut microbiome drive addiction?

New research suggests an imbalance of gut microorganisms may influence the likelihood of addiction and addictive behaviors by increasing the severity of withdrawal symptoms, triggering brain inflammation in regions of impulse control, and more.

Psychedelics set off a flurry of brain activity that may permanently alter it

The brain seems to experience a sharp increase in communication between areas that generally don't interact. New research suggests a thin, sheet-like gray matter structure tucked deep within the brain, between the insular cortex and striatum, may be the key to this change. The area is centrally located and home to many of the receptors that psychedelics target, potentially rewiring the brain and rewriting thought patterns.

The neuroscience of heartbreak

An analysis of functional MRIs revealed a difficult fact: the active brain areas of people experiencing heartbreak were very similar to those actively in love. This is a major reason why people in the middle of rejection can't accept the reality of their loss. This article breaks down the various changes in neurotransmitters and neural pathways for those enduring that universal experience, heartbreak.

How four types of psychedelics affect the brain

Brain imaging shows that ayahuasca, MDMA, DMT, and psilocybin profoundly affect neural activity, giving rise to higher states of introspection and consciousness. This article details exactly how each of these drugs physically affects the brain and what that means for mental health treatment. Some of these drugs quiet the brain or trigger the release of neurochemicals associated with mood regulation and learning.

Stress and the brain

While an acute stress response is a normal bodily function, the effects of chronic stress can be extremely damaging to the human body. This is particularly true with regard to the brain. This article explores the effects of stress on the human brain, including how chronic stress may lead to psychological conditions such as depression and memory loss.

The neurobiology of meaningfulness: the benefits of psychedelics

Psychedelics produce powerful emotions in its users, including a profound sense of meaningfulness. The philosopher William James called this sense "noetic" in the late 19th century, but for decades researchers avoided studying the effects of such drugs on the brain. However, the recent resurgence in psychedelic research has heightened interest in the relationship between this noetic sense resulting from the therapeutic use of drugs. Learn what researchers have found out here.

Anesthetics slow brain activity by promoting inhibitory neurotransmitters

Drugs like propofol and isoflurane increase activity at the GABA receptor, which opens chloride channels. These ions enter neurons and hyperpolarize them, making them less likely to fire. Dexmedetomidine instead blocks norepinephrine receptors in the brainstem to sedate patients.

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.

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.

Exercise releases chemicals that enhance cognitive function

Neurotransmitters like dopamine, serotonin, and norepinephrine, along with increased brain-derived neurotrophic factor levels, enhance a wide range of brain functions. New research demonstrates a direct link between movement and numerous cognitive benefits, including memory, learning, and stress resilience.

Prolonged stress impairs the prefrontal cortex

Burnout isn't just a feeling—it physically affects the brain. Prolonged stress impairs regions of the brain responsible for decision-making, emotional control, memory, and more. It can also lead to chemical imbalances, like reduced dopamine and norepinephrine levels, that worsen these effects.

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.

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.

Why so many people love roller coasters even though they’re scary

When a threat arises, it triggers our bodies to go into fight-or-flight mode and prepare for danger. However, when no obvious threat to our safety is present, this natural high can become enjoyable. Some people are more likely to enjoy these thrills based on factors like individual brain chemistry or physical health.

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.

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.

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.

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.

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

TikTok's personalized algorithm activates the brain's reward system

A 2025 Washington Post study found that 75% of the TikTok users it studied nearly doubled their time spent on the app within a month. Experts in design and psychiatry say this is due to the app's interface and algorithm, which, after learning about the user's preferences, recommend videos more likely to activate that person's dopamine reward system than non-personalized suggestions.

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.

Why are humans hooked on horror?

A haunted horror attraction in Denmark is regularly stalked by researchers of the world's only laboratory dedicated to understanding fear's good side. Fear is one of many human emotions that correspond to a physiological response. As fear rises, so do adrenaline, cortisol, and heart and breath rates. As it ebbs, the body is flooded with dopamine, a hormone and neurotransmitter associated with desire, learning, and motivation.

How burnout alters your brain

Stress is a normal part of everyday life, and it’s not necessarily all bad. But chronic stress—the kind that leads to burnout—can change the size and functioning of parts of your brain. It can alter the ability to make new brain cells and memories and even potentially modify your DNA.

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.