Human beings have been using drugs since time immemorial. From herbs found in nature to potent manmade compounds, humans use drugs for many reasons. A drug—a substance that has a physiological effect when introduced to the body—may be used medicinally. Some people take drugs simply to experience an altered mental state. Others may use drugs to escape or numb reality, which can lead to substance use disorders. This has prompted many researchers over time to study which drugs are most harmful to us.
What determines whether a drug is dangerous?
As you will see, many of the drugs on this list are legally manufactured for medicinal purposes—so when does a drug become dangerous? And how can we measure how harmful it is?
The answer is a complex one. Although there is an abundance of scientific studies that investigate the dangers of particular substances, ranking them is no easy feat without a definitive and multilayered metric to do so.
Perhaps Dr. Scott Phillips of the Washington Poison Center puts it best: “The dose determines the danger.” You might even venture to say that there are no inherently dangerous chemicals—only dangerous doses.
“The dose determines the danger.”
-Dr. Scott Phillips, Washington Poison Center
Indeed, just about anything we can ingest becomes unhealthy after a point. That’s why we’ve assembled a list of 31 drugs–unranked—and grouped them into eight categories. Whether you’re interested in becoming a substance abuse counselor or are simply curious to know more, read on to learn about their unique properties, potential for harm and even possible benefits.
Opioids take the lion’s share of drugs on our list. Opium is a substance that is naturally produced by the poppy plant Papaver somniferum and has been used for thousands of years primarily to relieve pain. Today we manufacture opium derivatives, called opioids, for this same purpose. Unfortunately, opioids are also highly addictive and potentially lethal. Overdose deaths involving opioids have been climbing since the 1990s, thrusting us into what many have called an opioid epidemic. The National Institute on Drug Abuse (NIDA) reports that 68,630 people died in the United States from an overdose involving any opioid in 2020 alone.
Heroin is an illegal opioid made from morphine. Users inject, sniff, snort or smoke heroin and report a “rush” or euphoric feeling as a result. Heroin can be highly addictive and lethal.
Heroin use and associated deaths were steadily increasing in 2007 and beyond, but have actually been in decline in recent years. For example, heroin-involved overdose death rates decreased nearly 7% from 2019 to 2020.
Some prescription opioids have effects that are similar to heroin, and research suggests that misuse of these prescription drugs could lead to heroin use, particularly after someone’s prescription has ended.
Krokodil is a relatively new synthetic opioid. Its use was first reported in Siberia in 2002 and has since then mostly appeared in Russia and European countries. Desomorphine is the active ingredient in Krokodil, a synthetic derivative of morphine. It can be manufactured at home with codeine, along with several other easily available additives, as a cheaper, more accessible alternative to heroin. Krokodil is currently very uncommon in the United States.
It is speculated that Krokodil gets its name from the way that desomorphine can turn users’ skin greenish and scaly, like a crocodile. For this reason, many refer to it as a “flesh eating” drug.
An opioid in itself, methadone is used to treat opioid use disorder (OUD), particularly heroin addictions. It is an opioid agonist which can reduce opioid cravings and withdrawal symptoms as well as blunts or blocks the effects of other opioids. Unfortunately, there is risk that users can develop a dependency or addiction to methadone itself.
Methadone is highly regulated and can only be administered in a medical setting, meaning street encounters with the drug are unlikely.
Buprenorphine is another opioid used to treat OUD. It is a partial agonist, meaning it is not as strong as a full agonist like methadone. Buprenorphine prescriptions, as with other drugs used to treat OUD, are typically paired with counseling and other support services to promote the best possible chances of preventing relapses.
Fentanyl has become a topic of note in the media recently, and for good reason—in 2017, 59% of opioid-related deaths involved fentanyl, compared to just 14.3% in 2010. Synthetic opioids such as fentanyl are currently the most common drugs involved in overdose deaths in the United States. In fact, 75% of all drug overdose deaths in 2020 involved an opioid.
Fentanyl is 50 to 100 times stronger than morphine. Its potency makes it an efficient additive to other drugs since it takes relatively little to produce a high. This can be incredibly dangerous to users who don’t realize the drugs they’re taking (such as MDMA, heroin, cocaine or methamphetamine) also contain fentanyl. As a result, their bodies aren’t used to the stronger opioid and the risk of overdose becomes higher.
Fentanyl is used medicinally to treat severe pain, especially after surgery, or to treat chronic pain in patients who have developed tolerances to other opioids. Fentanyl is responsible for the vast majority of opioid deaths, legal and illicit.
Under the trade name Opana®, oxymorphone is a full agonist opioid analgesic used to treat moderate to severe pain. It has a similar potential for abuse compared to other schedule II opioids such as hydrocodone and methadone. Oral prescriptions for oxymorphone increased from 268,536 in 2007 to about 1.2 million in 2012, then remained fairly steady for the next few years. Following the establishment of the 2016 Centers for Disease Control and Prevention (CDC) Guideline for Prescribing Opioids for Chronic Pain, the total oxymorphone prescriptions dispensed decreased to 192,556 in 2021.
Oxycodone is another potent opioid with a history of abuse in the United States and elsewhere. It made waves when it was released in 1996 under the brand name Oxycontin® because it claimed to offer pain relief for 12 hours, much longer than generic medications. On that promise, it became the best-selling painkiller in the United States. Sales went from $48 million in 1996 to almost $1.1 billion in 2000.
The promise of longer-lasting pain relief couldn’t hold up, though. A 2016 investigation by The Los Angeles Times reported that even before Oxycontin was released, clinical trials showed that many patients weren’t getting 12 hours of relief. Purdue Pharma (Oxycontin’s manufacturer) continued to heavily market the drug as such, and in order to remain consistent with their 12-hour promise, instructed doctors to prescribe stronger doses instead of more frequent ones. But this can come at a grave cost: stronger doses mean higher highs and lower lows—the perfect recipe for addiction.
Hydrocodone is yet another prescription opioid with a high potential for abuse. It’s also the most frequently prescribed opioid in the United States. Hydrocodone is prescribed in combination products such as Vicodin® (hydrocodone and acetaminophen). In addition to providing pain relief, hydrocodone is an antitussive (cough suppressant). Hydrocodone prescriptions that contain acetaminophen have an added risk of liver toxicity in high doses. Like all prescription opioids, overdoses are possible.
Codeine is a prescription opioid for mild to moderate pain and is also an antitussive like hydrocodone. Taking codeine comes with the same inherent risks as other prescription opioids, such as potential for addiction, overdose and withdrawals if you stop taking the medication suddenly after using it over a longer period of time.
Codeine is often found in prescription-strength cough syrups. Some people combine cough syrups with soda to create a concoction known as “syrup,” “lean,” or “purple drank.” Because codeine is an opioid, this mixture can be highly addictive. The associated health risks are compounded when combined with other depressants like alcohol.
Amphetamines and other stimulants
Stimulants are a class of drug that accelerates communication between our bodies and brains. As a result, they are often taken—whether medicinally or recreationally—for effects such as increasing focus, alertness, talkativeness, perceived sense of confidence, elevating one’s mood and more. Stimulants can also increase anxiety, muscle tension, nausea, heart rate and blood pressure, especially when taken frequently and/or at higher doses. Stimulants can also cause seizures, comas and even death.
Amphetamines are manufactured stimulants which may be used to treat conditions such as Attention-Deficit/Hyperactivity Disorder (ADHD) or narcolepsy. They are commonly prescribed under brand names such as Adderall®, Methylin®, Ritalin® and more. The ability for amphetamines to increase focus and attentivity are primarily why they are abused, particularly Adderall. Today, the largest age group of people who are abusing Adderall without a prescription or other medical need are young adults between 18 and 25 years old, the prime age for college students. Students often misuse Adderall as a study aid, and combining any amphetamine with other substances can be particularly unpredictable and dangerous.
Misuse of prescription amphetamines can induce psychosis in which the user may experience paranoid delusions, hallucinations and aggressive or violent behavior.
Methamphetamine is a powerfully addictive stimulant that is chemically similar to amphetamines. It increases the amount of dopamine in the brain, the feel-good chemical linked to the reinforcement of rewarding behaviors. It’s crystal form, commonly referred to as crystal meth, is the most potent and looks like glass fragments or shiny, bluish-white rocks.
The long-term effects of meth use are grim and often quite visible. They include extreme weight loss, dental problems, itching and skin sores, anxiety, confusion, memory loss, paranoia, hallucinations and more. More than 16,500 people died from methamphetamine overdoses in 2019. Deaths continue to rise from stimulant overdoses, mostly from methamphetamine.
Cocaine is an addictive stimulant derived from the coca plant which is native to South America. Indigenous peoples of South America have chewed coca leaves for their energetic high for thousands of years. As a street drug, it is a fine, white, crystal powder which is most often snorted and increases dopamine in the brain.
Cocaine generally has the same harmful effects as other drugs in the stimulant family, but it also has the added danger of being mixed with other, potentially more dangerous substances. Dealers often mix cocaine with cornstarch, talcum powder or flour to increase profitability, or even amphetamines or synthetic opioids like fentanyl. This can increase the possibility of addiction and overdose.
In the 1980s, crack cocaine (also referred to simply as crack) rose dramatically in popularity. It is made from combining cocaine with water and another substance, usually baking soda. The mixture is then boiled and cooled into a rock. It was created as cheaper alternative to cocaine and sparked a lot of controversy after the Anti-Drug Abuse Act of 1986. The Act set possession thresholds and criminal penalties at a weight ratio of 100:1 for crack versus regular cocaine powder. Opposers claimed the law was racist since crack users were more likely to be African-American. There has been a resurgence of cocaine use in the past two years.
Bath salts—not to be confused with products such as Epsom salts that people use while bathing—are a type of synthetic cathinone, manmade stimulants chemically related to cathinone, a substance found in the khat plant which is grown in East Africa and southern Arabia. Flakka is another similar synthetic cathinone. Synthetic cathinones are sold as cheaper substitutes for other stimulants, such as amphetamines and cocaine. These drugs also have the potential to be even more powerful, perhaps much so. In fact, some sources report that snorting a line of bath salts can be as potent as doing ten lines of cocaine at once.
Hallucinogens (also called psychedelics) are psychoactive substances which alter someone’s sensory perceptions and cognitive processes in distinct ways. They can cause hallucinations and/or dissociations, intensify feelings and sensory experiences, and alter one’s sense of time. The length of time one experiences these effects are commonly called “trips.”
Some hallucinogens are manmade while others are extracted from plants. Like many other drugs found in nature, some plant-based hallucinogens have been used by indigenous people for millennia to initiate spiritual experiences.
LSD—which stands for lysergic acid diethylamide—is a powerful manmade hallucinogenic drug derived from the ergot fungus. LSD was first synthesized in the 1930s and over time became a symbol of 1960s counterculture. The Central Intelligence Agency (CIA) experimented with LSD during the years of Project MK-Ultra (1950s-60s) because they believed it could be leveraged as a psychological weapon during the Cold War. It was eventually outlawed by the U.S. federal government in 1968.
LSD can cause trips that last up to 12 hours long. User experiences with the drug can vary immensely. Along with feelings of euphoria and pleasurable perceptual changes, some claim it can expand one’s consciousness, increase empathy and detach oneself from their ego. However, potent sensory changes can also trigger “bad trips,” where people experience disturbing hallucinations, paranoia, panic and confusion. This is thought to be more common in people who have or are predisposed to mental health issues.
Some mushroom species contain psilocybin, the active ingredient which can produce mind-altering effects very similar to LSD when ingested. These psilocybin mushrooms (also called “magic mushrooms”) can be found all around the world. They are often eaten raw or brewed into a tea. The effects of magic mushrooms can be especially unpredictable since it is difficult to create consistent dosages. Like LSD, bad trips are always a possibility. Trips typically last between four and six hours.
Beginning on January 1, 2023, Oregon became the first U.S. state to legalize magic mushrooms for adult use. Magic mushrooms have shown promising results in several studies for treating mental health issues such as depression, PTSD and end-of-life anxiety. One study on alcohol use disorder showed, for example, that pairing psilocybin use with talk therapy resulted in a significant decrease in the number of heavy-drinking days compared to participants that were not administered the drug. Magic mushrooms cannot be sold recreationally in Oregon and can only be used in therapeutic settings.
NBOMes are a group of synthetic hallucinogens more potent than LSD and may be falsely marketed and sold as such. They produce many of the same effects as LSD but have also been involved in reports of attempted suicide and violent behavior towards others. Overdoses can lead to such behavior, seizures or even comas.
Ketamine is a dissociative anesthetic that can cause hallucinations. Its dissociative qualities make users feel disconnected to their bodies and environment and can produce effects similar to those experienced on drugs like LSD. It’s produced commercially in many countries including the United States for its sedative effects on humans and animals. Ketamine is commonly abused in dance club and “rave” settings but has also been used to facilitate sexual assault.
Ketamine-assisted therapy has become a growing market in the last few years ever since the U.S. Food and Drug Administration (FDA) approved esketamine, a ketamine derivative. The drug has shown robust promise in treating mental health issues, including severe depression.
MDMA is a synthetic stimulant and hallucinogen, and therefore produces many of the effects associated with both drug families. “Molly” is used to describe MDMA in its crystalline powder form. It’s a common party drug or “club drug” which has also been described as an entactogen, a drug that can increase empathy and self-awareness. It increases the activity of dopamine, norepinephrine and serotonin in the brain, which explains its sought-after pleasurable effects which earned its second nickname, “ecstasy.”
Ecstasy is the tablet form of MDMA. Because of the manufacturing process and added ingredients necessary to make it into a tablet, many people mistakenly think that ecstasy is less pure than its crystal counterpart, molly. However, both forms of MDMA can be cut with other, more harmful chemicals such as bath salts or fentanyl and make them highly dangerous. MDMA on its own can be harmful too—high doses can affect temperature regulation, which can cause a spike in body temperature that can occasionally result in liver, kidney or heart failure, or even death.
MDMA may also cause serotonin syndrome, especially if taken with other drugs that increase serotonin in the brain like many antidepressant medications.
MDMA is currently undergoing clinical trials to test its efficacy in treating mental health issues such as severe depression, PTSD, end-of-life anxiety and more.
Over-the-counter (OTC) substances
We have access to a plethora of drugs at our local grocery stores and pharmacies. While this can be a good thing, there are inherent risks in consuming just about any substance, even if it is legal. Some of these drugs may fall into other categories too, but we’ve called them out here to highlight their hazardous accessibility.
Alcohol is another drug that has been consumed regularly by humans for thousands of years.
Evidence of ancient alcohol consumption is present in just about every corner of the world. Beer, for example, was a staple in ancient Mesopotamia, especially since the brewing process killed bacteria and waterborne disease which sometimes made it safer to drink than regular water from canals.
We understand much more about alcohol today, which can harm just about every organ and system in the human body. Despite its proliferation, legal status and accessibility, alcohol is a causal factor in more than 200 diseases and injury conditions. Every year, three million deaths worldwide result from harmful use of alcohol, which accounts for 5.3% of all global deaths annually. According to the 2019 National Survey on Drug Use and Health (NSDUH), 14.5 million people over the age of 12 had alcohol use disorder (AUD) in the United States, and less than 10% of people with AUD received any kind of treatment.
The plant that we know today as tobacco is native to North and South America. It was used and smoked by the ancient Maya of Central America, particularly for religious ceremonies. European explorers brought tobacco back to Europe after encountering the indigenous people of the “New World” who still used tobacco for religious and medicinal purposes.
Tobacco is addictive because it contains nicotine, but it’s the other chemicals found in or added to tobacco that make it so deadly. This toxic mixture of chemicals can cause numerous fatal lung diseases, cardiovascular disease, diabetes and a host of other serious health problems. Cigarette smoking is responsible for over 480,000 deaths per year in the United States, including about 41,000 deaths in nonsmokers from second-hand smoke. Tobacco use causes over seven million deaths globally every year.
Perhaps an even more disturbing trend is the rise of electronic cigarette (e-cigarette) use, especially among the nation’s youth. Though these products do not contain tobacco, they do contain nicotine and many of the same toxic chemicals that make tobacco products so harmful.
Kratom and its products refers to the herbal substance derived from the leaves of a tree native to Southeast Asia. It is commonly sold as a powder and can be purchased legally online and in many stores (usually smoke shops) in the United States. It produces opioid and stimulant-like effects, though much is still unknown about the chemical compounds related to kratom and its short- and long-term effects on health. Although it has not been approved by the FDA for this purpose, people report using kratom to mitigate drug withdrawal symptoms, particularly for opioids. Research is still being conducted on the safety of kratom as well as its potential therapeutic uses.
Caffeine is a central nervous system (CNS) stimulant and is the most widely taken psychoactive stimulant in the world. The drug is naturally found in coffee, tea and cacao beans, but it’s also added to a lot of sodas and energy drinks. People most often use caffeine to combat fatigue and drowsiness.
Caffeine powder has emerged more on the market lately and is available to consumers in bulk. Caffeine powder is caffeine in its most potent form and can pose serious health risks to consumers. Using it safely requires the consumer to measure a safe amount to ingest, which has much room for human error. One teaspoon of pure powdered caffeine can contain the same amount of caffeine as 28 cups of coffee—a toxic amount that could cause rapid heartbeats, seizures and even death. Caffeine is also combined with methamphetamine and known as yaba.
The term cannabinoids refer to chemicals that join to the cannabinoid receptors in the body and brain. The cannabis plant produces between 80 and 100 cannabinoids and over 300 non-cannabinoid chemicals.
The term cannabis denotes all products derived from the plant Cannabis sativa. It is most often referred to as marijuana, a cannabis product that contains a substantial amount of THC, a single type of cannabinoid that is primarily responsible for marijuana’s effects. These typically include feelings of relaxation and euphoria, spontaneous laughter, increased appetite and sociability but can also cause anxiety, paranoia and slower reflexes.
Marijuana is legal for recreational use in 21 states, which includes Washington D.C. and Guam. Another 17 states (including Puerto Rico) allow marijuana for medical use only. Studies show that cannabis can be helpful in treating rare forms of epilepsy, nausea and vomiting (especially due to chemotherapy), loss of appetite (a common side effect of many medications), chronic pain and more. However, regular use can be habit forming and affect brain health, lung health (if smoked regularly), mental health and more. Heavy and/or long-term marijuana use in adolescence can have serious consequences for brain development.
Spice or K2 is synthetic cannabinoid often called “fake weed,” though this name can be a bit misleading. Although it may be marketed as a safer alternative to marijuana, it can actually be over 100 times more potent than plant-based marijuana which makes its effects wildly unpredictable and more dangerous. Spice and other synthetic cannabinoids bind to the same brain cell receptors as THC, therefore producing many of the same effects as marijuana. The higher potency (and potential for other added chemicals) can also increase the chances of more unpleasant effects such as extreme anxiety, confusion, paranoia and hallucinations. Overdoses are possible and can cause toxic reactions in the body.
Inhalants refers to numerous different substances that are typically taken only by inhaling. They contain chemicals which have psychoactive properties when inhaled, even though most inhalants are easily bought or found in the home or workplace and are not intended for getting high. A few examples of inhalants that people may abuse include paint thinner, gasoline, felt-tip marker fluid, spray paint, butane, whipped cream aerosols and nitrites.
Most inhalants affect the central nervous system (CNS) and slow brain activity. Because inhaling these substances produces a high that usually only lasts a few minutes, people may try to inhale repeatedly to make the high last longer. Inhalants are mostly used by kids and teens because of their accessibility. Abusing inhalants can cause numerous long-term adverse health effects such as liver and kidney damage, delayed behavioral development, brain damage, hearing loss and more.
Nitrites are a type of medication that is often prescribed to treat chest pain. They allow blood vessels to expand and relax. For this reason, older adolescents and adults may misuse nitrites to improve sexual pleasure. This can also increase a person’s chances of engaging in other unsafe, risky sexual behavior which could increase the risk of contracting or spreading infectious diseases.
Opposite of stimulants are sedatives (also called depressants). As their name suggests, they have a sedating effect on the body by slowing communication within the central nervous system. Some other effects of sedatives include reduced inhibitions, enhanced mood, slowed reaction time and impaired judgement. At high enough doses, users may experience blackouts or memory loss, lose consciousness or overdose, which can result in coma or death.
Gamma-hydroxybutyric acid or GHB was approved by the FDA in 2002 under the brand name Xyrem® to treat the symptoms of narcolepsy including cataplexy (transient episodes of muscle weakness). Although some people abuse GHB to get high, it has earned a greater reputation for being a “date-rape” drug. It usually comes as a colorless, odorless liquid that can easily be slipped into victims’ drinks. Users can become uncoordinated, dizzy, forgetful, feel sick, black out, hallucinate and more. Combining GHB with other drugs such as alcohol greatly increases the chance of overdose.
Benzodiazepines are depressant drugs which may be prescribed to treat seizures, intense anxiety, panic attacks and insomnia. They are often prescribed under more familiar names such as Xanax®, Valium®, Klonopin® and more. It is not recommended that they are taken over long periods of time since they are prone to cause dependence when misused.
Barbiturates are a type of medication used to treat many of the same conditions as benzodiazepines such as seizures and insomnia, or may be used to induce pre-anesthesia sedation prior to a surgery.
Dependence and addiction to barbiturates are possible, and can cause users to experience mild to severe withdrawal symptoms if they attempt to get off these drugs. Barbiturates are commonly co-abused with stimulant drugs like methamphetamines or cocaine to counteract their “upper” effects.
The last drug on our list gets a category of its own for not falling neatly into any of the other categories we’ve already included.
Anabolic steroids are synthetic derivatives of the testosterone hormone. They may be prescribed for various reasons, such as repairing muscle loss caused by other diseases or for men who aren’t producing enough testosterone on their own. However, they are often abused to increase muscle mass for the sake of improving athletic performance and/or getting more fit. People who take anabolic steroids can experience a plethora of negative physical and psychological effects, including increased risk of heart attack or stroke, high blood pressure, infertility (in men), severe acne, aggressive behavior, mood swings, paranoia, and even hallucinations and delusions.
Are you or a loved one struggling with substance abuse and needing help?
The Substance Abuse and Mental Health Services Administration (SAMHSA) leads public health efforts to improve behavioral health nationwide and support people living with mental health and/or substance abuse disorders. SAMHSA’s National Helpline provides 24/7 free and confidential referrals and information about mental and/or substance use disorders, prevention, treatment, and recovery in English and Spanish, 365 days per year.
SAMHSA’s National Helpline 800-662-HELP (4357) TTY: 800-487-4889