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Updated: February 28, 2023

The 31 most harmful drugs

assortment of drugs from brown bottle

Written and reported by:

Kendall Upton

Staff Writer

In This Article

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.










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.




Synthetic cathinones


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.


Psilocybin mushrooms




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.






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.




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.



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.





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 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

For additional information on finding help and treatment options, visit SAMHSA’s website.

scott phillips md

Reviewed by and with professional insight from:

Dr. Scott Phillips, MD, FACP, FACMT, FAACT, Executive Director/Medical Director

Washington Poison Center