Hallucinogens: What Are They and What Are Their Effects?

The hallucinogen class of drugs includes a diverse group of substances capable of altering a person’s thoughts, perceptions, and mood. Historically, some hallucinogens have been used for spiritual reasons, and others have even been tested for use as medicines. Though hallucinogen-related substance use disorders are not as prevalent as those involving certain other substances of abuse such as alcohol and opioids, hallucinogen use does carry certain health risks and, in some cases, can lead to long-term problems.1

According to the 2019 National Survey on Drug Use and Health, 44,087 Americans 12 years old and older had used hallucinogens—a category that included classic hallucinogens like LSD, dissociative drugs such as PCP, and phenethylamines such as MDMA—some point in their lifetime.2 Many people who use hallucinogens may not be fully aware of their potential dangers. This article will explain some of the risks of abusing these substances.

What Are Hallucinogens?

Teen taking LSD

There are many different kinds of hallucinogens and each affects the brain in its own unique way. One relatively broad concept of hallucinogens encompasses two other substance classes: classic hallucinogens and dissociative drugs.1

Both classic hallucinogens and dissociative drugs can cause hallucinations (i.e. seeing or hearing things that are not there); however, dissociative drugs may also be more likely to result in a person sensing a loss of control or detachment from their own body and their surroundings.1

Types of Classic Hallucinogens

Classic hallucinogens are thought to elicit their effects by disrupting neurochemical signaling involving serotonin, a brain chemical that is central to a person’s mood, sensory perception, and other physiological processes.1

Some of the more widely-known classic hallucinogens are:1

  • D-lysergic acid diethylamide (LSD): One of the most famous of the mind-altering psychedelic chemicals, LSD was first synthesized in 1938 by the Swiss chemist Albert Hoffman while researching novel stimulant compounds for a pharmaceutical company. LSD has been researched extensively as a possible treatment drug for a variety of disorders.3 However, like all the classic hallucinogens on this list, the DEA classifies LSD as a Schedule I substance, meaning it has no accepted medical uses and a high potential for abuse.4 LSD is isolated as a clear or white odorless compound derived from ergot, a fungus that grows on grains.1,5
  • Peyote: The primary ingredient in this small cactus is mescaline. Sometimes called “buttons” or “cactus”, peyote has been used in healing and religious rituals in Central and North America for millennia. Mescaline is sometimes manufactured synthetically.1,16
  • Psilocybin: Psilocybin can be found in many species of mushrooms that are native to South America, Mexico, and the U.S.1 This hallucinogen, often called “shrooms” or “magic mushrooms” may be dried and either eaten or brewed into tea.6
  • Dimethyltryptamine (DMT): DMT has a number of natural sources, including the Amazonian plant species Virola. It can also be chemically synthesized. In powder form, it can be smoked, snorted or injected.7 Ayahuasca is a plant concoction brewed into a tea and consumed.8 Ayahuasca consumption for religious or ceremonial purposes dates back many centuries.7
  • 25I-NBOMe: Sometimes called “N-bomb,” synthetic hallucinogens such as 25I-NBOMe and 25C were originally developed for medical research but are abused for their hallucinogenic effects that are similar to MDMA and LSD but much stronger.1,9

Types of Dissociative Drugs

Many dissociative drugs work, in part, by interacting with N-methyl-D-aspartate (NMDA) receptors in the brain to disrupt activity within the glutamate neurotransmitter system.10 Glutamate is an excitatory neurotransmitter that plays a key role in several brain processes, including those involved with:10

  • Cognition (including memory recall and learning).
  • Emotion.
  • Pain perception.

The most common and well-known dissociative drugs are:1

  • Phencyclidine (PCP): Historically developed as a general surgical anesthetic, PCP (“angel dust”) produces intense dissociative effects and a euphoric rush.1,10 Because of its significant side effects (e.g., post-operative delirium and hallucination), it is no longer manufactured for medical use in the United States. PCP is commonly encountered in powder or liquid form but may also be sold in tablets or capsules.1  It can be smoked, snorted, swallowed, or injected.11 PCP is associated with a number of dangerous acute and long-lasting risks including violent behavior, fatal overdose and addiction.11, 12
  • Ketamine: Chemically similar to PCP, ketamine continues to have some limited medical use in both human and veterinary medicine. However, ketamine is also widely abused for its notorious dissociative effects.16 Dose-dependent effects include a sense of relaxation, immobility, and hallucinations.17 Someone who is experiencing an intense, immobilizing ketamine high is often said to be in a k-hole.18 As an illicit club drug, ketamine has reportedly been used to incapacitate others in date rape.1,18
  • Dextromethorphan (DXM): This drug is found in over-the-counter cold and cough preparations.  A person who misuses DXM at high doses may experience hallucinations, delusions, paranoia, and even psychosis, earning DXM the nickname “the poor man’s PCP.”15
  • Salvia: This potent hallucinogen has, like other plant-based hallucinogens, been used for religious rituals in Central America for many years.13  Salvia has a very different mechanism of action than many other dissociative drugs. Unlike the others listed in this section, its effects are mediated through activation of the kappa opioid receptor.10  Salvia is not federally regulated in the US (though some states have passed laws to curtail abuse of the drug). Despite its legality, this drug can be dangerous, causing intense and sometimes frightening hallucinations. Salvia can be smoked, chewed, or converted into vapor and inhaled.14

Short-Term Effects of Hallucinogens

While each drug is unique and experiences vary between individuals, there are several common effects seen with many of the classic hallucinogens and dissociative drugs. The experience of being under the influence of a hallucinogen is often called a “trip.”1 

Classic Hallucinogen Effects

Common short-term effects of classic hallucinogens include:1

  • Amplified emotions and senses.
  • Altered perception of time.
  • Increased heart rate, breathing, and blood pressure.
  • Uncoordinated movements.
  • Dry mouth.
  • Nausea.
  • Decreased appetite.
  • Problems sleeping.
  • Hallucinations.
  • Paranoia.
  • Other drug-induced psychotic features (e.g., disordered thought, detachment from reality).

The onset of these effects and how long they last is highly dependent on the drug used. For example, the effects of LSD are often felt within 20-30 minutes after taking an oral dose and can last up to 12 hours.19 In contrast, the powder form of DMT elicits effects almost instantly, and the high lasts only 15-60 minutes.8

Dissociative Drug Effects

Possible short-term effects of dissociative drugs include:1

  • Panic.
  • Disorientation.
  • Amnesia.
  • Symptoms of psychosis.
  • Problems with coordination.
  • Increased blood pressure and heart rate.
  • Numbness.
  • Immobility.
  • Difficulty breathing.
  • Seizures.

Like classic hallucinogens, the length of time these effects last is dependent on the drug used. For example, while most of the effects of salvia may wear off in less than 30 minutes, the effects of PCP tend to last up to 8 hours, with some people experiencing them for as many as 48 hours.14, 20

What Is a “Bad Trip”?

When someone has a prolonged negative experience while using hallucinogens, it is commonly referred to as a “bad trip”21

Bad trips can be extremely unpleasant and frightening experiences, and their occurrence is often quite unpredictable—it is not possible to guarantee a good trip on any hallucinogen. However, avoiding very high doses and remaining in a safe and secure environment can help to mitigate the risk. 22

If you’re with someone having a bad trip, you might try to help by getting them away from others and from too much stimulation such as loud noises. Continually reassure them that they are safe and that the high will wear off in time. 22

Can You Overdose on a Hallucinogen?

Though relatively rare, toxicity and overdose involving hallucinogens is possible. Overdose likelihood depends on the specific drug being used and the dose at which it is used. Fortunately, high doses of classic hallucinogens are very rarely life-threatening. One notable exception, however, is 25I-NBOMe, which has been the cause of medical emergencies and has even claimed the lives of several people.1

Dissociative drugs, on the other hand, carry a much more pronounced risk of toxicity and overdose. PCP and DXM have been known to cause seizures, coma, and death at high doses.1, 23 Ketamine abuse can also lead to a fatal overdose.24 

Even in the absence of overdose, a hallucinogenic experience can become dangerous. For example, a person high on hallucinogens may act bizarrely or become violent toward themselves or others.1,22 In some cases, hallucination intoxication can be fatal if someone takes risks they would never normally take (e.g., jumping from a high building) or acts on a suicidal impulse.1

What are the Long-Term Effects of Using Hallucinogens?

While rare, some long-lasting consequences of certain types of hallucinogen use have been reported, including: 1

  • Hallucinogen Persisting Perception Disorder (HPPD): HPPD causes an individual to re-experience some of the effects of past trips in the form of flashbacks. This can happen at any time without warning.
  • Persistent psychosis: Sometimes mental problems persist long after drug use. These problems may include:
    • Paranoia.
    • Mood changes.
    • Disorganized thoughts.
    • Visual disruptions.

While the long-term effects of many dissociative drugs continue to be studied,. However, PCP use is linked to risks including:11

  • Memory loss.
  • Problems thinking clearly.
  • Anxiety and depression.
  • Addiction.

Prolonged use of ketamine can result in:24,25,26

  • Chronic pain in the abdomen.
  • Bladder inflammation and irritation.
  • Liver injury.
  • Spatial memory loss.

Are Hallucinogens Addictive?

While hallucinogen use disorders involving classic hallucinogens like LSD are uncommon, any consistent use of these drugs can lead to the development of problematic, compulsive patterns of use and the health risks that accompany such use.21

Additionally, many of the dissociative drugs that we have discussed, such as PCP, have more pronounced addictive potential. Unlike the classic hallucinogens, some dissociative drugs are also associated with physical dependence and a distressing withdrawal syndrome that may benefit from medical management. 11, 27, 28

Regardless of whether a person may get addicted to these substances, the dangers of hallucinogens—both short-term and long-term—are real.1


  1. National Institute on Drug Abuse. (2019). Hallucinogens drugfacts.
  2. Center for Behavioral Health Statistics and Quality. (2020). Results from the 2019 National Survey on Drug Use and Health: Detailed tables. Rockville, MD: Substance Abuse and Mental Health Services Administration.
  3. Baquiran M. & Al Khalili Y. (2020). Lysergic Acid Diethylamide (LSD, Entactogen) Toxicity. Treasure Island (FL): StatPearls Publishing.
  4. Drug Enforcement Administration. Drug Scheduling.
  5. Hwang K.A.J. & Saadabadi A. (2020). Lysergic Acid Diethylamide (LSD). Treasure Island (FL): StatPearls Publishing.
  6. Drug Enforcement Administration. (2020). Psilocybin.
  7. Drug Enforcement Administration. (2019). N,N-Dimethyltryptamine. Drug & Chemical Evaluation Section.
  8. Barker S. A. (2018). N, N-Dimethyltryptamine (DMT), an Endogenous Hallucinogen: Past, Present, and Future Research to Determine Its Role and Function. Frontiers in Neuroscience12, 536.
  9. Drug Enforcement Agency. (2020). 25I-NBOMe, 25C-NBOMe, and 25B-NBOMe.
  10. National Institute on Drug Abuse. (2015). What are the effects of common dissociative drugs on the brain and body?
  11. U.S. National Library of Medicine. (2018). Substance use – phencyclidine (PCP).
  12. U.S. National Library of Medicine. (2020). Phencyclidine overdose.
  13. Mahendran, R. & Winslow, M. (2014). From divination to madness: features of acute intoxication with Salvia use. Singapore Medical Journal. 55(4), e52–e53.
  14. National Institute on Drug Abuse. Salvia.
  15. Birur, B. Black, J. R., Bolis, R. A., Fargason, R. E. & Martinak, B. (2017). Dextromethorphan in Cough Syrup: The Poor Man’s Psychosis. Psychopharmacology bulletin47(4), 59–63.
  16. National Institute on Drug Abuse. (2015). Common hallucinogens and dissociative drugs.
  17. Drug Enforcement Agency. (2020). Ketamine.
  18. Cohen S.P., Orhurhu V.J., Vashisht R. (2020). Ketamine Toxicity. Treasure Island (FL): StatPearls Publishing.
  19. U.S. National Library of Medicine. (2018). Substance use – LSD.
  20. Drug Enforcement Agency (2020). Phencyclidine.
  21. Miller, S. C., Fiellin, D. A., Rosenthal, R. N., & Saitz, R. (2019). The ASAM Principles of Addiction Medicine, Sixth Edition. Philadelphia: Wolters Kluwer.
  22. University of California Santa Cruz. (2019). LSD.
  23. U.S. National Library of Medicine. (2020). Dextromethorphan overdose.
  24. Utah Poison Control Center. (2015). Toxicology Today.
  25. National Institute of Diabetes and Digestive and Kidney Diseases (2018). LiverTox: Clinical and Research Information on Drug-Induced Liver Injury
  26. Dodds, C. M., Doeller, C., Fam, J., Freeman, T. P., Furby, H., Hughes, E. (2014). Long-Term Heavy Ketamine Use is Associated with Spatial Memory Impairment and Altered Hippocampal Activation. Frontiers in psychiatry, (5),149.
  27. National Institute on Drug Abuse. Cough and cold medicines.
  28. Lembke A., Prekupec M.P., Sher Y., Sussman R.S. (2017). Relapse on ketamine followed by severe and prolonged withdrawal: A cautionary case and review of potential medical therapies. J Nat Sci., 3(10), e450.




About The Contributor

Scot Thomas, M.D.
Scot Thomas, M.D.

Senior Medical Editor, American Addiction Centers

Dr. Thomas received his medical degree from the University of California, San Diego School of Medicine. During his medical studies, Dr. Thomas saw firsthand the multitude of lives impacted by struggles with substance abuse and addiction, motivating... Read More

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