By Edmund Murphy

Last updated: 22 May 2024 & medically reviewed by Hailey Shafir

Hallucinogens are mind and mood-altering drugs that cause people to hallucinate; seeing, hearing, and sensing things that aren’t there. While few people become actively addicted to these drugs, many people abuse them recreationally and some are unaware of their powerful and potentially hazardous effects.

Key takeaways:

  • Most classic hallucinogens may produce extremely unpleasant experiences at high doses, although the effects are not necessarily life-threatening
  • Some hallucinogens (like mescaline, peyote, and magic mushrooms) are extracted from plants, and some are synthetically made by humans (like LSD)
  • Research suggests that classic hallucinogens work at least partially by temporarily disrupting communication between brain chemical systems throughout the brain and spinal cord
Hallucinogens & Psychedelics

What are hallucinogens?

Hallucinogens are a diverse group of drugs that alter a person’s perception of their surroundings as well as their own thoughts and feelings. They are commonly split into two categories: classic hallucinogens (such as LSD) and dissociative drugs (such as ketamine). Both types of hallucinogens can cause hallucinations or sensations and images that seem real though they are not. Additionally, dissociative drugs can cause users to feel out of control or disconnected from their bodies and environment.[2]

Some hallucinogens (like mescaline, peyote, and magic mushrooms) are extracted from plants, and some are synthetically made by humans (like some forms of DMT). Historically, people have used hallucinogens for religious or healing rituals, and there are some active studies right now that are exploring whether certain hallucinogens can help people struggling with issues like depression, anxiety, and PTSD.[3] Still, the most common use of hallucinogenic drugs is recreational. People use hallucinogens to alter or enhance their experience of reality, some even promoting their use as a therapeutic medication when taken in small amounts. This is known as microdosing

Abusing hallucinogens

Hallucinogenic drugs are illegal substances and currently, are not FDA-approved for the treatment of any disorder. While most hallucinogens have low addictive potential, they are still widely abused in a recreational way, and can sometimes lead to adverse effects and experiences.

Because of the way that these drugs alter a person’s perception, they can lead people to have frightening and intense hallucinations (also called ‘bad trips’) that can be distressing or upsetting. Many hallucinogens also have long-lasting effects that can continue for 8-12 hours or longer, and for this duration, people are unable to make clear, rational decisions or function in a normal way.

Related: How long does LSD stay in your system?

How do hallucinogens affect the brain?

Research suggests that classic hallucinogens work at least partially by temporarily disrupting communication between brain chemical systems throughout the brain and spinal cord. Some hallucinogens interfere with the action of the brain chemical serotonin, which regulates:

  • mood

  • sensory perception

  • sleep

  • hunger

  • body temperature

  • sexual behavior

  • intestinal muscle control

Using hallucinogens and psychedelics in high doses or alongside antidepressants can cause an imbalance in serotonin levels which can lead to a life-threatening condition called serotonin syndrome.

Dissociative hallucinogenic drugs interfere with the action of the brain chemical glutamate, which regulates:

  • pain perception

  • responses to the environment

  • emotion

  • learning and memory

Related blog: Psychedelic Compound DMT Increases Connectivity In The Brain, Scans Reveal

Short-term effects of hallucinogens

As their name suggests, the most common side effect of hallucinogens is for the user to experience images, sounds, and sensations that appear real but are not. These hallucinations usually start within the first 20 to 90 minutes of taking the drug and can last as long as 12 hours or longer. Most people who take hallucinogens will refer to these sensations as ‘trips’, with negative reactions being classed as ‘bad trips’.

Along with hallucinations, other short-term general effects include:

  • Increased heart rate

  • Nausea, vomiting or GI distress

  • Intensified feelings and sensory experiences (such as seeing brighter colors)

  • Changes in sense of time (for example, the feeling that time is passing by slowly)

  • Mood changes including happiness, sadness, anxiety or paranoia

  • Restlessness, insomnia

  • Trouble focusing or thinking clearly

  • Impaired motor functioning

  • Impaired ability to make decisions

Specific short-term effects of some hallucinogens include:

  • Increased blood pressure, breathing rate, or body temperature

  • Loss of appetite

  • Dry mouth

  • Sleep problems

  • Spiritual experiences

  • Feelings of relaxation

  • Uncoordinated movements

  • Excessive sweating, hot and cold chills

  • Panic, paranoia or anxiety

  • Psychosis-disordered thinking detached from reality

  • Bizarre behaviors

Read more on staying safe while on LSD here.

Long-Term effects of hallucinogen abuse

There are few documented long-term effects resulting from hallucinogen use, but a small percentage of people do experience lasting changes in their perception and ability to think clearly. These rare symptoms are categorized as either persistent psychosis or HPPD.[1]

Persistent psychosis

A series of continuing mental problems, including:

  • visual disturbances

  • disorganized thinking

  • paranoia

  • mood changes

Hallucinogen Persisting Perception Disorder (HPPD)

Hallucinogen Persisting Perception Disorder (HPPD) refers to the recurrence of particular drug experiences, often hallucinations or visual disturbances, commonly referred to as ‘flashbacks’. These flashbacks can come without warning and will often happen within the first few days of use but can occur more than a year later. These symptoms can sometimes be confused with other disorders, such as brain tumors or strokes. 

Both conditions occur more frequently in those suffering from a history of mental illness, though they can happen to anyone, even after one use. Some behavioral therapies can be used to help people cope with fear or confusion associated with visual disturbances, and some antipsychotic medications can help with HPPD.

Hallucinogens drug dependence and addiction

There are relatively few documented cases of addiction to hallucinogenic drugs. People rarely abuse these drugs regularly because of their intense and long-lasting effects and the way these effects make daily functioning almost impossible. 

However, it is possible to abuse these drugs too frequently which can result in a number of different problems, including the build-up of drug tolerance (needing more to get the same effect) and impairment or consequences in one or more areas of life. While hallucinogens are not believed to be physically addictive, there are other signs and symptoms which may indicate a person has developed an unhealthy pattern of abuse or dependence, including: [4]

  • Taking the drug more often, in higher doses, or for longer than intended

  • Unsuccessful efforts to cut back or stop

  • Craving or desiring to take the drug

  • Spending a lot of time obtaining, using, or recovering from the effects of the drug

  • Problems in an important relationship because of using the drug

  • Impairment in work, home, or another responsibility because of drug use

  • Neglecting other enjoyable activities to use the drug more

  • Continuing to use despite negative health or mental health effects

Related blog: Psilocybin Can Alleviate Severe Depression For Up to 12 Weeks

Can someone overdose on hallucinogens?

Most classic hallucinogens may produce extremely unpleasant experiences at high doses, although the effects are not necessarily life-threatening. High doses of PCP can cause overdose and some of the lesser-used synthetic hallucinogens like 251-NBOMe have also resulted in fatalities. [1] Also, taking these drugs in combination with any other substance (including marijuana or alcohol) can also lead to serious, or even fatal, overdose. [1] 

More commonly used hallucinogens like LSD, mushrooms, and Peyote have not had documented fatalities. Still, using these drugs (especially in high doses) can lead to altered perception and impaired decision-making, placing people at risk. Those who consume psilocybin through magic mushrooms also run the risk of accidentally consuming poisonous mushrooms, which can result in seizures, illness, and death.

Common hallucinogenic and dissociative drug types

There are a variety of psychotropic drugs, some naturally occurring and some synthetic, each with its own particular effects and properties. the most common forms of hallucinogens are as follows:


Formally used as a form of psychiatric treatment, Lysergic acid diethylamide (LSD) is today a Schedule I drug.

LSD affects the serotonin levels in the brain, distorting the neurotransmitters associated with behavior, perception, and regulation. This causes hallucinations and causes the user to lose their sense of reality, an experience known as ego death.

Psychedelic mushrooms

Psychedelic or magic mushrooms are types of naturally occurring fungus that contain the drugs psilocybin or psilocin, chemically similar to that of the synthetic LSD. The effects of magic mushrooms can include heightened sensory experiences, impaired judgment, hallucinations, and a detachment from reality. The negative side effects include panic attacks, depression, frightening hallucinations, and terror. 

Mescaline (Peyote)

Long used by Native Americans, consuming mescaline found in the peyote cactus is one of the oldest forms of psychedelics still used today. Though some proclaim peyote to be effective in treating depression, it is still a Schedule 1 drug and illegal. Its side effects include vivid mental images, altered perception of time, and a distorted sense of the physical body.

Bath Salts

Bath salts do not have an exact chemical makeup as their production can change slightly from batch to batch. They are a concoction of various synthetic stimulants, mainly consisting of cathinone, a substance most commonly found in khat. They often cause hallucinations and adverse behavior which can endanger the user and others. Flakka is similar to bath salts yet is considered a stimulant

Salvia Divinorum

A psychoactive plant that can cause hallucinations and visions, Salvia Divinorum is currently legal in some places in the US. Most people claim it produces a sensation of flying and a dissociation of time, as well as dizziness, lack of coordination, and nausea. 


Originally used as an anesthetic for animals and humans, most illegal ketamine comes from veterinary offices. It can be snorted as a powder, ingested as a pill, and in some cases injected. In small doses, it can cause mild hallucinations and dissociative feelings, which become more intense and dangerous with higher doses.


DMT (N, N-dimethyltryptamine) is a powerful chemical found naturally in some Amazonian plants. People can also make DMT in a lab as well as from certain species of toad. Synthetic DMT usually takes the form of a white crystalline powder that is smoked.


MDMA is a stimulant and empathogen that also has hallucinogenic properties. While it is not a typical hallucinogen, it is sometimes combined with hallucinogens in what is commonly called a ‘trip roll’ to enhance its effects. MDMA can be dangerous and can lead to dangerous effects, overheating, stroke, and even fatal overdose.


Ayahuasca has been used for thousands of years as part of religious ceremonies in parts of South America. The substance is derived from the ayahuasca plant and is often brewed into teas that create powerful hallucinations when consumed.

2C-B (2C drugs)

2C-B is the most common form of 2C drug, an illegal substance that has both stimulant and hallucinogenic effects. This makes them popular amongst ravers and partygoers as they are reported to feel like a combination of MDMA and LSD.


Ibogaine is a psychoactive substance found in a plant from West Africa and a powerful psychedelic. It has been used as a traditional medicine and ceremonial plant for many centuries and is now believed to have potential benefits as a treatment for substance use disorders.

Get help for your addiction

Hallucinogens are rarely the ‘drug of choice’ for people who struggle with addiction but are sometimes a part of a larger problematic pattern of drug abuse. While there are current studies exploring the possibility of psychedelics to treat disorders like depression, anxiety, and PTSD, these drugs are not currently FDA-approved, and most are illegal to possess or use. Also, hallucinogens can have powerful and long-lasting effects that can cause distress, paranoia, and hallucinations, and are not recommended for recreational use. People who need help with a substance use disorder or addiction should set up an appointment with a licensed addiction specialist today to explore options for treatment.

Visit here for more information and guides about the effects of hallucinogen abuse.