Have your perceptions been

Hallucinogens can change the way you see things. The experience is a little like 

looking at the optical illusion below.

The Brain’s Response to

Hallucinogens

Hi, my name’s Sara Bellum. Welcome to 

my magazine series exploring the brain’s 

response to drugs. In this issue, we’ll 

investigate the fascinating facts about 

hallucinogens.

Hallucinogens cause people to experience 

—you guessed it—hallucinations, imagined 

experiences that seem real.

The word “hallucinate” comes from Latin 

words meaning “to wander in the mind.” No 

wonder some people refer to hallucinating as 

“tripping.”

The “trips” caused by hallucinogens can last 

for hours. Parts of these trips can feel 

really good, and other parts can feel 

really terrible.

Hallucinogens powerfully affect 

the brain, distorting the way 

our five senses work and changing our 

impressions of time and space. When people 

use these drugs a lot they may have a hard 

time concentrating, communicating, or 

telling the difference between reality and 

illusion.

The Brain’s Response to

Hallucinogens The Search Continues

The truth is, there’s still a whole lot that 

scientists don’t know about the effects 

of hallucinogens on the brain. Maybe

someday you’ll make the next big discovery.

Until then, join me—Sara Bellum—in 

the other magazines in my series, as we 

explore how drugs affect the brain and 

nervous system.

ALTERED?

National Institute on Drug Abuse Mind Over Matter is produced by the National Institute on Drug Abuse, National Institutes of Health, U.S. Department of Health and 

Human Services. These materials are in the public domain and may be reproduced without permission. Citation of the source is appreciated. 

NIH Publication No. 09-3858. Printed 1997. Reprinted 1998, 2000, 2003, 2005, 2006, 2007. Revised 2009.

For more information, visit:

www.teens.drugabuse.gov

To learn more about hallucinogens and other drugs of abuse, or to order materials 

on these topics, free of charge, in English or Spanish, visit the NIDA Web site at 

www.drugabuse.gov or contact the DrugPubs Research Dissemination 

Center at 877-NIDA-NIH (877-643-2644;

TTY/TDD: 240-645-0228).
Some hallucinogens can be found in plants. Mescaline comes 

from a cactus called peyote. And certain mushrooms, also 

known as “magic” mushrooms, are hallucinogens.

But many hallucinogens are chemicals that don’t 

occur in nature. Some examples are:

• LSD, also called acid

• MDA, also called the “love drug,” related to 

the stimulant amphetamine

• MDMA, know as ecstasy, also related to 

amphetamine

• PCP, often called angel dust

Where Do Hallucinogens Come From?

Your brain controls all of your perceptions—the way you see, hear, smell, taste, 

and feel. How does your brain communicate with the rest of your body? Chemical

messengers transmit information from nerve cell to 

nerve cell in the body and the brain. Messages are constantly being sent back and forth with amazing speed.

Your nerve cells are called neurons, and their chemical messengers are called neurotransmitters. When neurotransmitters attach 

to special places on nerve cells (called receptors), they cause changes in 

the nerve cells.

This communication system can be disrupted by chemicals like hallucinogens, and the 

results are changes in the way you sense the world around you.

How Hallucinogens

Affect Your Senses

PCP prevents the actions normally caused when a 

neurotransmitter, called glutamate, attaches to its receptor 

in the brain. It also disrupts the actions of other 

neurotransmitters.

This drug’s effects are very unpredictable. For 

example, it may make some people hallucinate 

and become aggressive, while others may become 

drowsy and passive. It is also addictive.

Actions of PCP in the Brain

LSD: The Most Commonly

Used Hallucinogen

LSD causes its effects mainly by activating 

one type of receptor for serotonin. Because 

serotonin has a role in many important 

functions, LSD use can have many 

effects. These may include sleeplessness, 

trembling, and raised heart rate and blood 

pressure. 

LSD users may feel several emotions at 

once (including extreme terror), and their 

senses may seem to get crossed—giving 

the feeling of hearing colors and seeing 

sounds.

Even a tiny speck of LSD can trigger these 

effects. And LSD has an unusual “echo”: 

many users have flashbacks—sudden 

repetitions of their LSD experiences—days 

or months after they stop using the drug. 

MDMA and MDA cause neurons to release a neurotransmitter called serotonin, which 

can overactivate serotonin receptors. Serotonin is important to many types of nerve 

cells, including cells that receive sensory information and cells that control mood, sleep, 

and memory. Animal studies have taught us that MDMA and MDA can damage fibers 

from these nerve cells. And even though some of these fibers grow back, they don’t 

grow back normally. They can wind up in places where they don’t belong.

How MDMA and MDA Affect Your Brain