Updated on February 6, 2024
11 min read

What Are Illicit Drugs?

Key Takeaways

What are Illicit (Illegal) Drugs?

Illegal drugs, also called illicit drugs, are highly addictive substances that are illegal to sell, make, and use. These drugs are not used for medical purposes and are illegal to use in these settings.

In other words, patients cannot get prescribed illicit drugs by a doctor. You will most likely get arrested for using illegal drugs like:

  • Heroin
  • Ecstasy
  • Cocaine
  • Hallucinogens
  • Marijuana (in some places)

These drugs are highly addictive and have severe side effects that can lead to long-term health consequences. You can also die of an overdose.


Online Therapy Can Help

Over 3 million people use BetterHelp. Their services are:

  • Professional and effective
  • Affordable and convenient
  • Personalized and discreet
  • Easy to start
Find a Therapist

Answer a few questions to get started

Woman drinking coffee on couch

List of Illegal Drugs

Commonly misused illicit drugs include:


Amphetamines are a class of synthetic drugs that have stimulant properties. Being central nervous system stimulants, the use of amphetamines results in increased alertness and wakefulness.

They're also used recreationally due to their euphoric and pleasurable effects. The Drug Enforcement Agency (DEA) has categorized them as Schedule II substances. This means it has a high potential for abuse and addiction.

Anabolic-Androgenic Steroids

Steroid addiction can affect the body long after they are no longer used. This is especially true when taken by adolescents.

Doctors prescribe steroids to boost testosterone levels in the body for men who are out of balance. People who abuse steroids take doses up to 100 times the prescribed amount or use more than one type of steroid at a time.

Bath Salts

Synthetic cathinone or "bath salts" are a type of human-made drug with stimulant effects. The drug has similar effects to drugs like MDMA or amphetamines.

Bath salts can be swallowed, snorted, or injected. The effects usually last up to 8 hours.

Club Drugs

"Club drugs" is a broad term referring to many different categories of drugs of abuse and several individual drugs within each category. Club drugs are any drugs young people use to enhance their experience at a social gathering.

Many club drugs are synthetic or mixtures of different drugs. They are sometimes referred to as "designer drugs."

Crystal Meth

Meth is a form of methamphetamine that has a glass or rock-like appearance. It affects the central nervous system and is highly addictive. Meth has side effects that are similar to other stimulants, like cocaine.

The effects are usually felt quickly and last several hours after use. Meth is an illegal drug classified as a Schedule II substance.


Cocaine is considered a Schedule II drug, which means it has a high potential for abuse. It's illegal to sell as a street drug because of its addictive nature and harmful effects.

A study from 2014 found about 1.5 million people (12 and older) were past-month cocaine users. The more an individual uses, the more at risk they are of developing an addiction.


Ecstasy is a synthetic, psychoactive drug classified as a stimulant. Its main ingredient is MDMA, scientifically known as 3,4-methylenedioxymethamphetamine.

Ecstasy typically comes in pills that users swallow, although it can be crushed and snorted. It gives the user an intense high and keeps them awake for hours, which is why it's such a popular party drug.

In the United States, it is a Schedule I drug with no accepted medical use in treatment. Find out how long Molly stays in your system.


Flakka is classified as a Schedule 1 synthetic drug by the U.S. Drug Enforcement Administration. The synthetic drug may be:

  • Eaten
  • Injected
  • Snorted
  • Vaporized in e-cigarettes

The euphoric high from flakka abuse can last hours to days, depending on the dosage. The drug has been linked to several deaths by suicide and heart attacks.

Freebasing Drugs

Freebasing is a method of using a drug, usually cocaine, to increase its potency. It is a clear sign of drug abuse.

In this method, the user puts the base form of the drug in a glass pipe and heats it until it boils. Then, they inhale the vapors for a faster, more intense high.


GHB (gamma hydroxybutyrate) is a potent central nervous system (CNS) depressant drug. It occurs naturally in tiny quantities in the human brain as a neurotransmitter. In the U.S., GHB is used in one prescription drug (Xyrem) that has been approved by the FDA for treating cataplexy or excessive daytime sleepiness in people with narcolepsy.


Opium poppy plants, grown in Columbia, Mexico, and Southern Asia, yield morphine. Pure heroin is a white powder and is usually "cut" with sugar, powdered milk, starch, or quinine.

Many people use heroin intravenously. The effects of heroin are fast-acting and powerful. Users get an intense "rush" of intense pleasure that lasts for a few minutes.

The high continues for another four to five hours as the drug works through the bloodstream. 1 in 4 first-time users become addicted.


Marijuana is a green mixture of dried flowers and leaves from the Cannabis plant. It's a psychoactive drug that triggers a dopamine release in the brain, producing a "high." The drug is legal for recreational use in 11 U.S. states and D.C. for adults over 21.


PCP is a dissociative hallucinogenic, different from class 1 hallucinogens, such as:

  • Psilocybin
  • LSD
  • Peyote
  • DMT

The effects of PCP make it possible for the brain to disconnect from "normal" sensory experiences. The suspension of all legal PCP manufacturing occurred in 1979, and the drug is now only made in illegal drug labs.

PCP users sometimes experience elevated negative side effects, called a "bad trip." Bad trips induce paranoia, hostility, anxiety, and a feeling of impending doom

Performance Enhancing Drugs

Performance-enhancing drugs (PEDs) are drugs taken to improve physical performance. Elite athletes often use these drugs despite restrictions in sports and laws against the use of some of these drugs.


Phenibut is a nootropic drug with a structure similar to gamma-aminobutyric acid (GABA). GABA is a neurotransmitter known to:

  • Reduce anxiety and excitability
  • Induce calm
  • Promote relaxation
  • Enhance cognitive function
  • Euphoria


Speed is a white powder that has no odor and a bitter taste. It can also be smoked like crack cocaine when it is in crystal form, called "crystal meth."

Speed users experience three times the amount of dopamine as compared to cocaine. People with a speed addiction are prone to violence and hallucinations. They may also sometimes display symptoms similar to schizophrenia.

Speed use can also damage the cells in the brain that contain dopamine. This can lead to symptoms like Parkinson's disease.

Speedball (Heroin & Cocaine)

A speedball combines heroin and cocaine. Heroin is a depressant, while cocaine is a stimulant. The combination creates a 'push-pull' reaction in the brain and body, generating an intense high.


Spice is a blend of lab-manufactured mind-altering chemicals. The drug is illegal, but manufacturers can sometimes avoid the law by altering the mixture of ingredients.

Manufacturers tend to alter the ingredients to avoid drug laws, making it impossible to know how safe the end product is. There is no way to be sure what chemicals are in a spice dose or synthetic cannabinoid.

Get Professional Help

BetterHelp can connect you to an addiction and mental health counselor.

Find a Therapist

Answer a few questions to get started

Rehab Together

Side Effects & Dangers of Illicit Drug Use

Illicit drugs are very dangerous to your health, which is why they are illegal. A higher tolerance for a drug also increases your risk of:

  • Overdose
  • Addiction
  • Drug-related health issues

Depending on the type of illicit drug being used, the side effects and risks can vary:


Marijuana, commonly called weed or pot, is a green mixture of dried flowers and leaves from the Cannabis plant. It's a psychoactive drug that triggers dopamine release in the brain, producing a “high” and heightened sensory perception. 

Side effects can include:

  • Red and/or dry eyes, which is due to the blood vessels in the eyes expanding
  • Altered senses (for example, seeing brighter colors)
  • Altered sense of time
  • Changes in mood
  • Difficulty with attention and problem-solving
  • Trouble concentrating
  • Impaired memory
  • Increased heart rate
  • Reduced reaction time
  • Burning mouth and throat (when smoking marijuana)
  • Eating more often than normal
  • Tiredness

Cocaine and Crack

Crack is the freebase form of cocaine, which is an extremely addictive central nervous system (CNS) stimulant. Cocaine is a white crystal powder generally snorted, dissolved, and injected. 

Common risk factors associated with long-term crack abuse include:

  • Psychosis
  • Delirium
  • Chronic depression
  • Mood disorders
  • Extreme paranoia, irritability, and aggression
  • Heart attack
  • Heart disease
  • Stroke
  • Brain seizures
  • Coughing and shortness of breath
  • Lung trauma and bleeding
  • Respiratory failure
  • Sexual dysfunction
  • Infertility and damage to reproductive organs
  • Drug dependence and high tolerance (even after one use)
  • Death (from health complications or an overdose)

Stimulants and Amphetamines

Stimulants are drugs that increase activity, alertness, interest, and enthusiasm. They increase activity in the central nervous system (CNS).

All stimulants are addictive and can lead to serious health issues if misused. Common side effects and dangers of stimulant use include:

  • Feelings of euphoria 
  • Increased heart rate and blood pressure
  • Increased alertness
  • Increased talkativeness
  • Reduced appetite
  • Anxiety
  • Tension
  • Increased body temperature
  • Nausea
  • Tremor
  • Seizures
  • Coma
  • Stroke
  • Overdose
  • Death


Psychedelics are also referred to as “hallucinogens.” Users of these drugs usually do not experience addiction symptoms, such as withdrawal and drug-seeking behavior.

Although these drugs are not addictive, they can cause serious short and long-term side effects. Some users may be susceptible to having a “bad trip,” and experience highly adverse reactions, including:

  • Frightening hallucinations
  • Intense confusion
  • Severe disorientation
  • Paranoia
  • Frantic agitation
  • Extreme sadness
  • Panic or terror
  • Psychosis


People who use narcotics like heroin, codeine, morphine, and opium can develop a dependence. This increases the likelihood of an overdose that can lead to convulsions, coma, and death.

Heroin, for example, is one of the most addictive drugs on the planet. Side effects and dangers of heroin use include:

  • Dry mouth
  • Warm flushing of the skin
  • Heavy feeling in the arms and legs
  • Nausea and vomiting
  • Severe itching
  • Clouded mental functioning
  • Going “on the nod,” a back-and-forth state of being conscious and unconscious
  • Higher likelihood of contracting HIV or other bloodborne diseases 
  • Insomnia
  • Collapsed veins 
  • Damaged tissue inside the nose
  • Infection of the heart lining and valves
  • Liver and kidney disease
  • Lung complications
  • Mental illness
  • Sexual issues
  • Addiction
  • Accidental overdose and death

Why are Certain Drugs Illegal?

Certain drugs are illegal to sell, make, and use because they have extremely harmful properties, including physical and psychological harm. Some substances can permanently damage a person's brain if used long-term and excessively, such as methamphetamine.

This is the reason why there are laws put in place to prevent the misuse of illicit drugs. Illegal drugs can also result in:

  • Poor choices
  • Bad behavior
  • Aggression
  • Driving under the influence
  • Drug-related injuries or deaths
  • Murder

Criminal behavior related to illicit drug misuse is a huge problem worldwide.

Some research shows that about 65 percent of the U.S. prison population has a substance use disorder (SUD). Another 20 percent did not meet the official criteria for a SUD but were under the influence of drugs or alcohol when they committed their crime.


Phone, Video, or Live-Chat Support

BetterHelp provides therapy in a way that works for YOU. Fill out the questionnaire, get matched, begin therapy.

Get Started

Answer a few questions to get started

Woman drinking coffee on couch

Why are Illicit Drugs Addictive?

Most drugs affect the brain’s reward system, causing euphoria and flooding the brain with the neurotransmitter dopamine. Increased dopamine levels cause the reinforcement of pleasurable but unhealthy behaviors like taking drugs, which leads people to continue the behavior.

As a person uses drugs, the brain adapts by reducing the ability of cells in the reward center to respond to it. When this change occurs, they'll feel less high than when they first took the drug, otherwise known as tolerance.

A higher tolerance might make someone:

  • Take more of the drug to achieve the same high
  • Derive less pleaser from other things they've enjoyed
  • Experience unpleasant withdrawal symptoms

How Do Illicit Drugs Negatively Affect Someone's Life?

Illegal drugs can negatively impact a user's life in many ways.

Some of the most common include:

  • Neglecting work and daily responsibilities due to drug use
  • Low motivation to go to classes (dropping grades)
  • Financial problems and spending a lot of money to obtain drugs
  • Relationship damage (partners, families, and friends)
  • Legal issues (arrests, fines, violence, stealing, etc.)
  • Health issues and risk of overdose
  • High risk for addiction

Signs of Illicit Drug Misuse & Addiction

Children, teens, and adults are all at risk of illicit drug misuse and addiction. If you suspect your loved one is on drugs, there are signs to look for.

Symptoms of substance use disorder (SUD) include one or more of the following symptoms within 12 months:

  • Recurring substance use that causes the user to fail to fulfill significant role obligations at work, school, or home 
  • Regular substance use in situations in which it is physically hazardous such as driving or operating heavy machinery
  • Legal problems caused by substance use
  • Continuing to use a substance despite social or interpersonal problems caused or made worse by the effects of the substance 

Signs of Illicit Drug Use in Teenagers

If you suspect a teenager is abusing drugs or alcohol, look for the following signs:

  • Sudden mood swings and changes in behavior
  • Getting in trouble for misbehaving
  • Declining grades
  • Being late or absent from school
  • Inability to stop drinking once they start
  • Hiding drugs, alcohol, or paraphernalia
  • Feeling tired, disinterested, or angry with life
  • Not stopping using drugs or alcohol despite getting in trouble
  • Borrowing and stealing money
  • Giving up old hobbies, sports, activities, or friends for drugs or alcohol
  • Using eye drops or mouthwash to hide symptoms of drug or alcohol use
  • Health problems
  • Getting in trouble with the police

What Illegal Drugs Cause Liver Damage?

Chronic use of certain illicit drugs like heroin and inhalants has been linked to liver damage. The damage can worsen if you combine these substances with other drugs or alcohol.

What Illegal Drugs Cause Heart Damage?

Crack, cocaine, amphetamines, methamphetamine, and other illicit stimulant drugs can cause heart problems. This is because these drugs constrict the heart's blood vessels, making the organ work faster to pump blood.

This can lead to:

  • Heart rhythm issues
  • Heart attack
  • Stroke

Get matched with an affordable mental health counselor

Find a Therapist

Answer a few questions to get started

Updated on February 6, 2024
13 sources cited
Updated on February 6, 2024
  1. Alcohol Questions and Answers.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 16 Feb. 2021.

  2. Amphetamines.” DEA, Drug Enforcement Administration.

  3. Assistant Secretary of Public Affairs (ASPA). “What Are Opioids?” HHS.gov.

  4. National Institute on Drug Abuse. “Cocaine.” NIDA.

  5. Kampman, K.M. “New Medications for the Treatment of Cocaine Dependence.” Psychiatry (Edgmont (Pa.: Township)), Matrix Medical Communications, 2005.

  6. National Institute on Drug Abuse. “Cocaine.” NIDA.

  7. National Institute on Drug Abuse. “Methamphetamine.” 2019.

  8. "Drugs of Abuse." 2017 ed., U.S. Dept. of Justice, Drug Enforcement Administration, 2017.

  9. Johnson et al. “Psilocybin Dose-Dependently Causes Delayed, Transient Headaches in Healthy Volunteers.” Drug and Alcohol Dependence, Johns Hopkins University School of Medicine, Department of Psychiatry and Behavioral Sciences, Behavioral Biology Research Center, 2012.

  10. Studerus et al. “Acute, Subacute and Long-Term Subjective Effects of Psilocybin in Healthy Humans: A Pooled Analysis of Experimental Studies.” Journal of Psychopharmacology, 2011.

  11. Berke, J. “Legal Marijuana Just Went on Sale in Illinois. Here Are All the States Where Cannabis Is Legal.” Business Insider, Business Insider, 2020.

  12. Marijuana Use Disorder Is Common and Often Untreated.” National Institutes of Health, U.S. Department of Health and Human Services, 2016.

  13. National Institute on Drug Abuse. “Is Marijuana Addictive?” NIDA.

Related Pages

What Are Illicit Drugs?

What is Freebasing?

Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.

What Are Illicit Drugs?

What Is Flakka?

Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.

Are You Addicted to Stimulants? Signs & Symptoms

Adderall Addiction

Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.

What Are Illicit Drugs?

How to Choose the Right Rehab for You

Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.


How Long Does Molly Stay In Your System?

Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.

Addiction Resources


Learn about the different types of illegal drugs, their effects on the body, and how to get help for addiction.