Illicit drugs are illegal to make, sell or consume. Many illicit drugs are highly addictive and dangerous. Learn more about the risks of illicit drug abuse.

Illicit Drugs Hotline

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What Are Illicit Drugs?

Illicit drugs are defined as substances that are illegal to possess, have no medical applications and can be dangerous to consume. To answer the question, “What are illicit drugs?” most illegal drugs are unregulated substances like heroin, cocaine and marijuana, but this term also encompasses prescription drugs that are acquired illegally and chemically compromised, like fentanyl, which is often combined with heroin.

The uses and safety implications of prescription and illicit drugs are evaluated by the Drug Enforcement Administration (DEA), which categorizes drugs into schedules based on their medical applications and abuse potentials. These categories range from schedule I drugs, which are substances with high abuse potentials and low medical values, to schedule V drugs, which are non-addictive drugs with proven medical uses. Most illegal drugs, including heroin, LSD, marijuana and ecstasy, are labeled schedule I, although some illicit substances, like cocaine and methamphetamine, are categorized as schedule II drugs. 

As their DEA schedules explain, most illicit drugs are not safe for medical or recreational purposes and can be addictive. Illegal drug use can have severe consequences, including addiction and overdose. People who are dependent on drugs may need professional treatment to overcome a substance use disorder.

Dangers of Illicit Drugs

The use of illegal drugs is dangerous at best and deadly at worst. Illicit drug use can be a perilous gamble for numerous reasons, including: 

  • Many illegal drugs are highly addictive
  • Illegal drugs are unregulated, meaning their potency is often unknown, or undisclosed
  • Many drug dealers “cut,” or mix, illicit substances with other dangerous drugs
  • Injecting illegal drugs can raise a person’s risk of contracting diseases like HIV and hepatitis

A person who uses illegal drugs also risks becoming dependent on the substances they use. It is possible for someone to develop a physical tolerance to illicit drugs, meaning that over time they will need to take larger quantities of the drugs to achieve the same effects. However, taking large amounts of any drug, prescription or illicit, can result in a fatal overdose or spur a long-term substance use disorder which may require rehab. Despite these dangers, illicit substance abuse is a major issue in America. 

Statistics on Illicit Drug Use

Each year, the Substance Abuse and Mental Health Services Administration compiles comprehensive data on drug use in America. Their annual report, the National Survey on Drug Use and Health, explains the current prevalence of substance use disorders and mental illnesses, and includes statistics on illicit drug use and prescription drug abuse. According to the most recent survey data,illicit drug use is a complex and growing problem in the United States.

At a Glance: Illicit Drug Use in America

According to national data, in 2017: 

  • More than 30 million Americans used illicit drugs
  • Roughly 1 in 9 people engaged in illegal drug use within the month prior to the survey
  • Approximately 2 million people were currently using cocaine, with 473,000 people using crack cocaine
  • An estimated 594,000 young adults ages 18–25 used hallucinogens like ecstasy, LSD and ketamine
  • Although 494,000 people were currently using heroin, 652,000 Americans had a heroin use disorder
  • Nearly 1 in 5 young adults, ages 18–25, were using marijuana
  • Almost 964,000 Americans had a methamphetamine use disorder

Types of Illicit Drugs

There are several different types of illicit drugs and each has different effects on the body. Illicit drugs examples include stimulants like cocaine, narcotics like heroin, hallucinogens like LSD, and depressants or sedatives.

A comprehensive list of illegal drugs and unregulated substances may include:

Is My Loved One Addicted to Illicit Drugs?

If you’re worried that someone you love may be addicted to an illegal drug, this quiz can help you match behaviors that your loved one may exhibit to common signs of illicit drug addiction. Take The Quiz


Drug class: Stimulant

DEA classification: Schedule II

Common names: Coke, snow, blow, white, dust, or powder 

Popularized by movies and TV shows, cocaine sometimes appears to be the ultimate party drug. However, this illegal drug is highly addictive and is often mixed with other harmful substances like boric acid, amphetamines and local anesthetics. As a white powder, cocaine can be snorted, smoked or injected. The drug releases a rush of dopamine in the brain, followed by a debilitating crash. People who use cocaine repeatedly can develop a cocaine use disorder and may need to seek professional treatment to overcome this addiction. 


Drug class: Stimulant

DEA classification: Schedule II

Common names: Rocks, candy, gravel, dice, or snow coke

As a type of crystallized cocaine, crack is produced by mixing cocaine powder with water, ammonia and baking soda. This variant of cocaine can be tan or yellow in appearance and may resemble rock candy. Crack is often smoked in crack pipes and can be just as addictive as powder cocaine, if not more so. Given that an addiction to crack cocaine can have life-threatening consequences, rehab is advisable for anyone who struggles with this kind of substance use disorder.


Drug class: Stimulant

DEA classification: Schedule I

Common names: Molly, XTC, Adam, candy, beans, dancing shoes, or love drug

Ecstasy is the common name of the synthetic drug 3,4-methylenedioxy-methamphetamine or MDMA. As a popular club drug, ecstasy is often abused for its psychoactive and hallucinogenic effects and serotonin-boosting abilities. Ecstasy can look like colorful candies or embossed tablets and is normally ingested orally. Short-term effects of ecstasy can include an elevated mood and increased energy, and MDMA may be less addictive than other illegal stimulants.


Drug class: Opioid

DEA classification: Schedule I

Common names: Dope, junk, H, smack, tar, skag, horse, or brown sugar

As one of the drugs that spurred the American opioid epidemic, heroin is one of the most commonly abused opiates and was responsible for 15,948 overdose deaths in 2017. Derived from the opium poppy plant, heroin can be a powder or a substance resembling black tar. Whether heroin is injected or smoked, it binds to the brain’s opioid receptors to create a euphoric high. Heroin is extremely addictive, and its use can lead to a debilitating substance use disorder. Rehab for heroin addiction is often necessary for people who use this illicit drug.


Drug class: Psychoactive hallucinogen

DEA classification: Schedule I

Common names: Weed, pot, kush, ganja, bud, grass, or Mary Jane

Cannabis, or marijuana, is one of the most widely used, and controversial, illicit substances in America. Marijuana is considered less dangerous than the majority of illegal — and even legal — drugs and has been legalized for medical and recreational use in some states. Derived from the cannabis plant, marijuana can be smoked in its dried leaf form, baked into foods or ingested as an oil. The active chemical in cannabis, delta-9-tetrahydrocannabinol, or THC, produces euphoric, relaxing and psychoactive effects. However, marijuana use can be dangerous, and marijuana use disorders often require comprehensive treatment.


Drug class: Stimulant

DEA classification: Schedule II

Common names: Meth, ice, crank, or chalk

Commonly referred to as meth, or crystal meth, methamphetamine is a highly addictive type of amphetamine. Often created in illegal drug labs, meth can be a crystalline substance that is clear or blue, and is often snorted, smoked or injected. All forms of meth stimulate the central nervous system and cause the brain to produce unnatural amounts of adrenaline and dopamine. Given that meth can be up to three times as potent as cocaine, people who use this drug can develop methamphetamine use disorders and may need to seek rehab to overcome a meth addiction.

Treatment for Illicit Drug Abuse

Drug addiction is a chronic disease that often requires professional treatment. Detox clinics, substance abuse counselors and outpatient facilities have different levels of treatment for illicit drug abuse, but rehab centers, like The Recovery Village, offer the most comprehensive care. Drug and alcohol rehab facilities often provide a variety of progressive programs, which allows clients to transition from one level of care to the next as they progress through therapy. This allows them to overcome addiction safely and effectively. 

A continuum of illicit drug treatment programs can include: 

If you struggle with an addiction to illegal drugs or know someone who needs help for a substance use disorder, don’t hesitate to seek help. The Recovery Village has locations across the country and offers flexible rehab programs that can be customized to meet your unique mental and physical needs.

Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.