Hallucinogens

What Are Hallucinogens?

Hallucinogens are mind-altering substances that can change a person's perceptions, thoughts, mood, and sense of reality. People may experience hallucinations, see or hear things that are not there, or perceive familiar sights, sounds, and sensations differently. Hallucinogens can also affect judgment, emotions, and behavior, increasing the risk of injury or other harmful consequences.

Some hallucinogens occur naturally in certain plants and mushrooms, while others are made in laboratories. Depending on the substance, hallucinogens may be swallowed, eaten, smoked, inhaled, snorted, or injected.

In 2024, an estimated 73.6 million people aged 12 or older reported using an illicit drug in the past year, including 10.4 million who reported using hallucinogens, 2.4 million of whom were young adults (ages 18 to 25). Use of hallucinogens has been on the rise in the U.S. in recent years.

Types of Hallucinogens

Hallucinogens include several different types of substances that affect the brain in different ways. Common examples include:

Classic psychedelics

LSD (lysergic acid diethylamide)
Psilocybin (magic mushrooms)
Mescaline
Peyote

Dissociative drugs

PCP (phencyclidine)
Ketamine

Other substances with hallucinogenic effects

MDMA (ecstasy or molly)

Some products sold as hallucinogens may contain unexpected or unknown substances, increasing the risk of harmful effects.

How Hallucinogens Affect the Body and Brain

The effects of hallucinogens vary depending on the substance used, the amount taken, the person's health, and whether other drugs or alcohol are used at the same time.

Short-term effects

Hallucinogens may cause:

Changes in perception, including seeing, hearing, or feeling things that are not present
Changes in mood or emotions
Altered sense of time or surroundings
Difficulty thinking clearly or making decisions
Confusion or disorientation
Anxiety, fear, or panic
Dilated pupils
Increased heart rate and blood pressure
Increased body temperature
Sweating or flushing
Nausea or vomiting
Loss of appetite
Tremors
Trouble sleeping

Some people may become agitated or behave in ways that put themselves or others at risk.

Long-term effects

Repeated use of some hallucinogens may lead to ongoing physical, psychological, or social problems. These may include:

Difficulty with work, school, or relationships
Problems with memory, attention, or concentration
Anxiety or depression
Ongoing mental health symptoms in some people
Continued use despite negative consequences

A rare but recognized condition called Hallucinogen Persisting Perception Disorder (HPPD) can cause recurring visual disturbances after the drug's immediate effects have worn off. Symptoms may include flashes of light, halos around objects, or other visual changes that interfere with daily life.

Can Hallucinogens Lead to a Substance Use Disorder?

Although not everyone who uses hallucinogens develops a substance use disorder, some people may develop a hallucinogen-related disorder characterized by repeated use despite harmful consequences. In 2024, an estimated 433,000 people had a past-year hallucinogen disorder.

Signs that someone may need help include:

Difficulty controlling or reducing use
Spending a great deal of time obtaining or using the substance
Continuing to use despite physical, emotional, or relationship problems
Problems meeting responsibilities at work, school, or home
Continuing to use even when it causes distress or interferes with daily life

Overdose and Other Medical Emergencies

The risk of overdose varies depending on the specific hallucinogen. Some substances, particularly when mixed with other drugs or alcohol, can cause life-threatening medical emergencies.

Seek emergency medical care or call 911 immediately if someone who has used a hallucinogen:

Has trouble breathing
Becomes unconscious or cannot be awakened
Has a seizure
Experiences severe agitation or violent behavior
Has a very high body temperature
Appears confused, delirious, or unable to respond
May have taken an unknown or counterfeit substance

Many drugs sold as hallucinogens may contain other substances that increase the risk of poisoning or overdose. Because it can be difficult to know what a product contains, any serious reaction should be treated as a medical emergency.

Prevention and Safety

To reduce the risk of harm:

Never use unknown or counterfeit substances
Avoid mixing hallucinogens with alcohol or other drugs
Do not drive or operate machinery after using a hallucinogen
Be aware that products sold illegally may contain unexpected substances
Seek medical attention immediately if someone experiences severe or unusual symptoms after using a hallucinogen

Parents, caregivers, schools, and communities play an important role in preventing substance use. National research indicates that many people first begin using hallucinogens during the high school or young adult years, making early conversations about substance use an important part of prevention.

Need Help?

If you or someone you know is struggling with substance use, help is available.

Talk with a healthcare provider or mental health professional.
Visit FindTreatment.gov to locate treatment services in your area.
Call the SAMHSA National Helpline at 1-800-662-HELP (4357) for free, confidential treatment referral and information, available 24 hours a day, 7 days a week, in English and Spanish

References and Relevant Resources

Last Updated: 08/03/2026