What Are Hallucinogens?

Male face silhouetted in sky as if a hallucination

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Hallucinogens are a class of drugs that cause profound distortions in a person's perceptions of reality, otherwise known as hallucinations. While under the influence of hallucinogens, users might see images, hear sounds, or feel sensations that seem to be real but aren't.

Hallucinogens, also known as psychedelics, work by disrupting how neurotransmitters work in the brain. Many hallucinogens have chemical structures similar to those of natural neurotransmitters, like acetylcholine, serotonin, or catecholamines.

Hallucinogens can be man-made, or they can come from plants or mushrooms or extracts from plants and mushrooms. Generally, they are divided into two types: classic hallucinogens and dissociative drugs. Either type of hallucinogen can cause users to have rapid, intense emotional swings.

This article discusses the different types of hallucinogens and their effects. It also covers how they work and their potential therapeutic uses.

Classic Hallucinogens

Some of the classic hallucinogens include:


Sometimes called hoasca, aya, and yage, ayahuasca is brewed from plants containing DMT along with an Amazonian vine that prevents the normal breakdown of DMT in the digestive system. It is usually consumed as a tea.


Dimethyltryptamine, also known as Dimitri or DMT, is a natural chemical found in some Amazonian plant species, but it can also be chemically synthesized. It usually comes as a white, crystalline powder that is vaporized or smoked in a pipe or bong.


D-lysergic acid diethylamide (LSD) is a manmade chemical made from ergot, a fungus that grows on certain grains. It is probably the most powerful hallucinogen available, producing hallucinations, changes in the way reality is perceived, and altered moods.

It comes as a white powder or clear liquid and has no color or smell. It can come in capsules, but most often comes on small squares of blotter paper or gelatin that users place on the tongue or swallow to take a "trip."


Methylenedioxymethamphetamine (MDMA) is a synthetic drug that is derived from amphetamine. It is also known as ecstasy or "molly." It works by increasing the activity of the neurotransmitters dopamine, serotonin, and norepinephrine. It acts as both a hallucinogen and a stimulant and produces enhanced sensory perceptions, decreased anxiety, and feelings of mental stimulation.


This natural substance is the main ingredient in the peyote cactus. The top of the spineless peyote cactus plants has disc-shaped "buttons" that contain mescaline. The buttons are dried out and then either chewed or soaked in liquid to produce an intoxicating drink. Mescaline can also be made through chemical synthesis.


Psilocybin and psilocin are natural substances found in hallucinogenic mushrooms. In large enough doses, psilocybin can produce effects very similar to the powerful hallucinogen LSD. "Shrooms," as they are sometimes called, can be used either fresh or dried. They are normally eaten, mixed with food, or brewed like tea for drinking.

Tetrahydrocannabinol (THC)

The active ingredient in marijuana is delta-9 tetrahydrocannabinol or THC, which acts on cannabinoid receptors found in brain regions that influence learning, memory, appetite, coordination, and pleasure.

THC is just one of more than 400 different active substances—and 60 different cannabinoid molecules—contained in marijuana. Widely used as a recreational and medicinal substance, marijuana has been found to cause paranoia or anxiety as well as hallucinations, especially in adolescents who use the drug regularly. Time distortion, which is a symptom of marijuana use, is also part of hallucination.


Classic hallucinogens include ayahuasca, DMT, LSD, MDMA, mescaline, psilocybin, and THC.

Dissociative Drugs

Dissociative drugs are a class of hallucinogens that affect the perception of sight and sound. In addition to causing these perceptual distortions, they also produce feelings of dissociation and detachment from the environment and/or the self.

Dextromethorphan (DXM)

Dextromethorphan, also known as DXM or robo, is a cough suppressant and expectorant that is often included as an ingredient in over-the-counter cold medications. When taken in doses higher than recommended, it may produce hallucinogenic effects including perceptual disturbances, feelings of euphoria, and disruptions in motor control.


Ketamine, also known as K or Special K, is a type of dissociative drug that is used as an anesthetic in humans and animals. When used recreationally, it often creates a deep dissociative state as well as visual disturbances, disorientation, euphoria, and sedation.


PCP is a dangerous manmade substance that was originally developed as an anesthetic but was discontinued for human use in 1965 due to side effects. It is now an illegal street drug sold as a white powder or in liquid form. It can be snorted, injected, smoked, or swallowed.

It produces hallucinations and "out-of-body" sensations. Usage, especially in large doses, can be life-threatening and lead to serious mental health problems.


Salvia is a hallucinogenic herb that is sometimes used recreationally to mimic the effects of LSD and ecstasy. Salvia is fast-acting, with effects that don't last long. Salvia contains a chemical called salvinorin A, which acts on receptors in the brain to produce hallucinations. When using the drug, people may experience dissociation, an altered sense of reality, and changes in self-awareness.


Some hallucinogens are classified as dissociative drugs. These include DXM, ketamine, PCP, and salvia.

How Hallucinogens Work

Scientists are not sure exactly how hallucinogens and dissociative drugs produce their effects. However, classic hallucinogens are thought to affect neural circuits in the brain involving the neurotransmitter serotonin, and dissociative drugs cause their effects by primarily disrupting the actions of the brain's glutamate system.

The regions of the brain that are affected by hallucinogens control mood, sensory perception, sleep, hunger, body temperature, sexual behavior, and muscle control.

Effects of Hallucinogenic Drugs

Hallucinogens can produce a range of effects that vary in terms of intensity, duration, and long-term effects. These drugs affect how people think, including their perceptions of reality and the self.

Short-Term Effects

The short-term effects of hallucinogens typically begin within 20 to 90 minutes of taking substances. These effects may be brief, lasting around 15 minutes in some cases. In other cases, these short-term effects may last as long as 12 hours.

Common short-term effects include:

  • Anxiety or panic
  • Changes in appetite
  • Changes in the perception of time
  • Feelings of euphoria or relaxation
  • Increased heart rate
  • Intensified sensory experiences and emotions
  • Nausea
  • Paranoia
  • Psychosis
  • Sleep disturbances

Long-Term Effects

Hallucinogens may also produce long-term effects in some cases. According to the National Institute on Drug Abuse, these effects are rare.

  • Hallucinogen persisting perception disorder (HPPD) involves the recurrences of experiences associated with using the drug including visual disturbances and hallucinations. Such flashbacks can occur suddenly with no warning and may occur more than a year following drug use.
  • Persistent psychosis may occur in some cases. Symptoms include mood changes, paranoia, disorganized thinking, and visual disturbances. 

Therapeutic Uses

There has been a resurgence of interest in the therapeutic potential of some hallucinogens. Psychedelic therapy is a type of treatment that uses psychedelic substances such as LSD, psilocybin, and ketamine in a controlled setting under the supervision of a therapist. 

Studies suggest that such substances may be helpful for treating some mental health conditions. For example, one study found that psilocybin combined with behavioral interventions was helpful for relieving anxiety and depression.


Hallucinogens are drugs that alter thoughts, perceptions, and feelings. While using these substances, people may experience hallucinations, where they have sensations or perceptions that are not real.

Experts do not know exactly how hallucinogens produce their effects, but they are believed to affect neurotransmitters in the brain, including serotonin and glutamate. Research also indicates that some hallucinogens may have therapeutic potential in the treatment of conditions such as anxiety and depression.

If you or a loved one are struggling with substance use or addiction, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

Frequently Asked Questions

  • What is the difference between narcotics and hallucinogens?

    Narcotics are drugs that include opiates, opioids, and synthetic opioids. Some of these drugs have medical uses, particularly for pain relief. They can also produce physical dependence and have a high potential for addiction. While hallucinogens affect thinking and perception, narcotics tend to produce a variety of effects including blocking pain signals and creating feelings of euphoria.

  • How do hallucinogens affect the brain?

    According to the National Institute on Drug Abuse, hallucinogens are believed to produce their mind-altering effects due to disruptions in the neurotransmitter serotonin. By altering how serotonin acts on neural circuits in the brain, particularly in regions associated with perception, mood, and cognition, people experience changes in how they think and perceive reality.

  • What is the difference between hallucinogenic and psychedelic?

    Hallucinogens and psychedelics are the same. Psychedelic is another word for hallucinogenic, meaning affecting thinking, senses, perceptions, and emotions. 

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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