The term ‘hallucinogens’ refers to a type of drug with psychoactive effects. They work by altering both mood and sense perception. Hallucinogens are also known as psychedelics. Whilst these drugs may be associated with the hippy culture of the 1960s and 1970s in the popular imagination, hallucinogens have been used ‘in indigenous medical traditions for millennia.’

Hallucinogen use has appeared to regain traction in recent years, with peak usage in 2019 in the United States. In one year, 5.5 million adults used some form of hallucinogens.
But where do hallucinogens come from? How do their psychedelic effects manifest, and what are the potential risks involved in using this family of substances?

Names for hallucinogens

Hallucinogens (also known as psychedelics) are known by a variety of names. These can be chemical or medical names, or they can be more colloquial street slang. Street names can differ between areas – you may find that the terms for drugs in America differ from those in the UK (You may also find that they change in different areas of England).
Some common street names for hallucinogens include:

  • Acid
  • Ecstasy
  • Fry
  • Mind Candy
  • Mushrooms
  • Shrooms
  • Special K
  • STP
  • X
  • XTC
DMT Addiction
Dimethyltryptamine (DMT) is a powerful psychedelic compound that naturally occurs in many plants and animals. It is typically consumed by smoking or vaporizing, though it can also be ingeste…

DMT Addiction

LSD Addiction
Lysergic acid diethylamide (LSD) is a potent hallucinogenic drug known for its profound psychological effects. It is typically administered orally, often in the form of blotter paper, but it can al…

LSD Addiction

PCP Addiction
Phencyclidine (PCP), also known as ‘angel dust’, is a powerful dissociative anesthetic that affects the central nervous system. Originally developed for medical use as an anesthetic, PCP is …

PCP Addiction

What do hallucinogens do?

Hallucinogens cause a range of sensory distortions in the user. The effects of a hallucinogen high are unique to the individual user – you may find that you have a different experience from a friend using the same hallucinogen. Similarly, you may find that your second use may feel completely different to your first.

Common effects of a hallucinogen high

Psychological effects:

  • euphoria: an intense rush of positive feelings 
  • feeling very relaxed and at ease 
  • hallucinations (auditory, visual, gustatory, tactile and olfactory hallucinations can all be experienced)
  • distorted perception of space and time 
  • distorted perception of your own body
  • decreased spatial awareness and coordination  
  • some cognitive deficits (feeling confused, struggling to pay attention)
Physical effects:

  • feeling (or being) sick 
  • decreased sensation in the body, as though physically numb 
  • altered vision (including blurring)
  • increased heartbeat 
  • increased blood pressure 
  • palpitations 
  • faster breathing 
  • difficulties with homeostasis (alternating states of overheating and shivering or chills)

These symptoms are associated with a ‘typical’ hallucinogenic high.

Bad trips

There are instances where people can respond to hallucinogens very differently. These symptoms are less pleasant and are often referred to as a ‘bad trip.’

  • feeling anxious
  • feeling afraid
  • feeling paranoid
  • particularly potent, distressing hallucinations

Hallucinogenic experiences can trigger psychological distress and increased physical harm risk. Heightened fear and diminished inhibitions may lead to unsafe reactions, risking harm to oneself and others. Bad trips, characterised by cognitive distortion, paranoia, and aggression, can result in out-of-character violent behaviour, occasionally escalating to serious crimes. A 2020 Vice article linked at least 11 homicides to ‘acid’ use. Research suggests women, especially in mushroom use, may be more prone to bad trips. It’s crucial to note that these effects aren’t universal, sporadically occurring in the typical use of hallucinogens.

Are hallucinogens legal?

Hallucinogens are generally not legal. There are different types of hallucinogens, however, which means that the drug classification of each drug may be slightly different.

Types of hallucinogens

There are several different types of hallucinogens. These are all used in different contexts, and have different pharmacological effects and mechanisms of action. This means that the high side effects and addictive potential of different hallucinogens may vary somewhat.
Some hallucinogens are naturally occurring and can be found in plants and fungi. Others are synthetic substances which are created in labs through specific chemical processes.

Some examples of drugs with hallucinogenic properties include:

All of these drugs act in different ways and, therefore, create different effects.


Ketamine is a type of hallucinogen known as a dissociative anaesthetic. Its main effect can be to make people feel ‘detached from their pain and environment.’ Ketamine has been used in medical and veterinary contexts as an anaesthetic since the 1960s. However, since the 1990s, the recreational use of ketamine has gained popularity.

Ketamine’s street names include:

  • K
  • Ket
  • Special K
  • Super K
  • Vitamin K 
Recreational use of ketamine typically causes the following effects:

  • provokes feelings of calm and relaxation 
  • acts as an analgesic (numbs pain)
  • provokes hallucinations 
  • increase in blood pressure and heart rate
  • numbness in the muscles 
  • memory loss
  • depression 
  • affected speech; slurring or poverty of speech

Ketamine facts:

The effects of ketamine take between 15 to 20 minutes to act. These effects can last for between 30 and 60 minutes.

Under the Drug Misuse Act of 971, ketamine is considered to be a Class B drug, meaning possession of ketamine could lead to up to 5 years in prison and an unlimited fine.
The legal consequences for the supply or production of ketamine are more severe, with the potential penalties of up to 14 years in prison or an unlimited fine being imposed.

Ketamine is understood to have some addictive potential; however, this risk is not thought to be as high as with some other hallucinogens. The World Health Organization (WHO) has repeatedly chosen not to include ketamine on the list of internationally controlled Drugs. This decision indicates that ketamine’s status as a globally accessible anaesthetic is perhaps more of an immediate concern than its abuse potential at present.


LSD is short for Lysergic Acid Diethylamide, also known by its street name ‘acid’. LSD is a powerful hallucinogen. Lysergic acid is naturally occurring – it can be found in a range of ergot alkaloids. Because of its connection to the synthesis of LSD, ergot is referred to as a ‘psychoactive fungus that changed history.’

LSD was initially synthesised by chemist Albert Hoffman in 1938, when his experiments on lysergic acid led to the development of LSD-25. It was not until five years later that Hoffman fully understood the powerful nature of the substance. Hoffman notes the psychedelic effects of the drug after accidentally being exposed to it in his lab.

Early experiments by Sandoz Chemical (the company Hoffman worked for at the time) investigated the effects of the drug in order to assess its utility in psychiatric contexts.

LSD’S street names include:

  • Acid
  • Blotter
  • Dots
  • Drop
  • Liquid Acid
  • Lucy
  • Micro Dot
  • Tab
  • Tripper
  • Trips
  • Window
An LSD high typically provokes the following symptoms:

  • euphoria 
  • changes to perception
  • pupil dilation 
  • increased heart rate 
  • arrhythmia 
  • temporary delusions 
  • hallucinations (auditory and visual)
  • confusion and disorientation
  • difficulty maintaining attention
  • nausea and being sick 
  • difficulty maintaining internal temperature 
  • faster respiratory rate 

LSD facts

The effects of LSD take between 20 minutes and 2 hours to act. These effects can last for between 6 and 12 hours.

It is rumoured that the CIA used LSD in clandestine experiments in America in the 1950s and 1960s to investigate the effects of LSD in psychochemical warfare.
LSD is a Class A drug. This means that it is considered to be one of the more dangerous substances available through illicit channels.

Possession of LSD could lead to up to 7 years in prison and an unlimited fine. The legal consequences for the supply or production of LSD are more severe, with the potential penalties of up to life in prison or an unlimited fine being imposed.


Mushrooms or ‘magic mushrooms’ are specific mushrooms that naturally grow in specific habitats. The most common types of these mushrooms in the UK are liberty caps (psilocybe semilanceata) and fly agaric (amanita muscaria).

  • Liberty caps: Liberty caps are common mushrooms that grow in the autumn months. They are small, brown specimens with a pronounced ‘nipple’ at the top of the cap. Wild Food UK asserts that the picking, preparing, eating and selling of liberty caps has been prohibited since 2005.
  • Fly agaric: Fly agaric looks like the typical ‘cartoon’ mushroom. They are a bright, vivid red in colour and have white spots. Fly agaric growth between August and December. This type of mushroom is ‘considered toxic but not deadly.’ There are supposedly ways to treat this mushroom to make it safe for consumption. However, the knowledge of how to do so is not widespread.

A key danger with magic mushrooms is that they often look very similar to other forms of mushrooms that are poisonous. Consuming such mushrooms can have toxic effects, leading to serious health complications or even death.

Street names or slang for mushrooms include:

  • agaric 
  • amani
  • liberties
  • liberty caps
  • magics
  • mushies
  • philosopher’s stones 
  • shrooms
Being high on mushrooms can lead to:

  • euphoria 
  • pupil dilation 
  • changes to perception 
  • temporary delusions 
  • hallucinations (auditory and visual)
  • increased body temperature 
  • increased heart rate 
  • arrhythmia 
  • pain or ache in the stomach
  • headaches 
  • feeling or being sick
  • increased respiratory rate 

Mushroom facts:

The effects of mushrooms can take 30 minutes or more to act and can last for anywhere up to 5 hours.

Mushrooms are Class A drugs. This means that, like LSD, the possession, supply or production of mushrooms can lead to serious legal consequences.

The possession of mushrooms could lead to up to 7 years in prison and an unlimited fine. The legal consequences for the supply or production of mushrooms are more severe, with the potential penalties of up to life in prison or an unlimited fine being imposed.

The main psychoactive agent in mushrooms is psilocybin.

MDMA / Ecstasy

MDMA, short for (3,4-methylenedioxymethamphetamine), is commonly known as ecstasy. It is usually obtained in powder form when purchased as MDMA and in tablet form when bought as ecstasy.

Initially synthesised in 1912 during a search for a medication to control heavy bleeding, MDMA was found to have strong psychoactive effects. During the Cold War, it was utilised as a psychoactive weapon in the CIA’s ‘MK-Ultra’ project in the 1950s, investigating the potential of specific psychoactive drugs for mind control.

In the 1970s, MDMA was promoted as a pharmacological support for certain psychiatric conditions. Its recreational popularity surged in the 1980s with the emergence of the rave scene.

MDMA street names:

  • Crystal
  • Dizzle
  • E
  • MD
  • MDMA
  • Mandy
  • Molly
  • Pills
  • X
  • XTC
An ecstasy high produces a range of effects, including:

  • Feelings of euphoria or ‘ecstasy’
  • High energy levels 
  • Strong feelings of connection with the people around them 
  • Heightened awareness of sensations (such as music and lights)
  • Dilated pupils
  • Tingling in the body 
  • Increased body temperature 
  • Increased heart rate 
  • Arrhythmia 
  • Nausea and being sick

It is also possible for people to experience counterintuitive or paradoxical effects of MDMA. These include strong feelings of anxiety, paranoia, confusion, panic attacks and potential psychosis.

Facts about ecstasy:

Ecstasy’s effects can be felt between 20 and 30 minutes after use. These effects can last for between 2 and 4 hours.

Ecstasy is also a Class A drug, meaning it incurs the same legal penalties as LSD and mushrooms: up to 7 years in prison for possession, and up to life for supply and production. Offences relating to possession, supply or production of MDMA can also incur an unlimited fine.


PCP is short for Phencyclidine or Phenylcyclohexyl piperidine. The drug has sedative and hallucinogenic qualities, which makes it quite similar to another dissociative anaesthetic, ketamine. PCP was first synthesised in the 1950s. It was used as an anaesthetic for some time due to its sedative effects and ability to numb pain.

However, PCP use was quickly discontinued. This is because physicians found their patients were experiencing a range of adverse effects, including becoming ‘agitated, delusional, and irrational.’

In medical practice, PCP was administered intravenously. In recreational use, PCP can be used in powder, tablet or capsule form.

Street names for PCP include:

  • Angel dust
  • Animal tranquilliser 
  • Embalming fluid 
  • Hog
  • Ozone 
  • Peace pills
  • Phencyclidine 
  • Rocket fuel
  • Whack
A PCP high may provoke the following effects:

  • Changes or distortions to reality 
  • Feeling numb, dissociated or ‘outside’ of your own body 
  • Hallucinations (auditory and visual)
  • Temporary delusions 
  • Changes in perception of time 
  • Extreme mood changes (causing euphoria or an intense low)
  • Feelings of paranoia 
  • Becoming more aggressive or violent than usual 

PCP facts:

PCP is commonly referred to as the ‘predecessor’ to ketamine. In fact, ketamine was supposedly produced in order to ‘replace’ PCP in specific contexts.

The speed and duration of PCP’s effects depend on a range of factors, including method of use, metabolism and if PCP is part of polydrug use.

PCP is a Class A substance, meaning that the same laws regarding LSD, mushrooms and ecstasy also apply to the possession, supply and production of PCP: 7 years in prison for possession, up to life in prison for selling and supply. These offences can also lead to unlimited fines.

Hallucinogens: How they work

The category of hallucinogens encompasses a diverse range of drugs, including both natural and synthetic substances, each with its unique mechanism of action. Despite the variability, psychedelic drugs, in particular, contain distinct psychoactive agents. For instance, psilocybin is the psychoactive agent in mushrooms.
These psychoactive agents exert their effects on specific areas of the brain. Recent research on psychedelics suggests that hallucinogens activate the serotonergic system and enhance glutamatergic transmission.

Hallucinogens and serotonin

The British Psychological Society explains that all ‘classic’ hallucinogens stimulate the same receptor in the brain – the serotonin receptor. In particular, these types of drugs engage with a receptor known as serotonin 2A. They can stimulate this receptor by copying the activity of serotonin chemicals.
Serotonin is a neurotransmitter, a naturally occurring chemical that exists within our brains. Our levels of serotonin are affected by several factors:

  1. The amount of serotonin produced by the brain
  2. The amount of serotonin interacting with receptor sites
  3. External forces that can increase serotonin levels

Serotonin is sometimes known as the ‘happy chemical’ because it has been associated with general wellbeing and balanced mood. The development of the serotonin deficit hypothesis indicates that depression can be related to a lack of serotonin activity in the brain.
This means that hallucinogens can enter the brain and begin to act like serotonin. In this manner, they can ‘sit’ into serotonin receptor sites (such as receptor 2A). This not only mimics the action of serotonin in the short-term but also changes the function of the receptor site in the long term.

Hallucinogens can have an excitatory effect on these neurons, meaning that they are much more active than is typical. This can chronically alter the way that the receptor site responds to serotonin.

Hallucinogens and glutamate

Hallucinogens have a second key effect on the neurotransmitters in our brains. They can work by ‘increasing glutamate spillover.’ Glutamate is a key neurotransmitter, sometimes known as ‘the master neurotransmitter.’ Glutamate works by exciting the cells of the brain. This means that they can work at a faster, more consistent level than is typical.
Research has indicated that high levels of glutamate could potentially be linked to high levels of anxiety and risk of seizures due to excess electrical activity in the brain. By causing ‘glutamate spillover’, hallucinogens can act to increase the excitatory nature of the neurotransmitter, causing the brain to work faster and harder.


Both of these types of actions interfere with the complex systems of the brain. This can lead to the development of positive symptoms such as hallucinations and delusions. Hallucinations happen when someone perceives something that others around them do not. You can experience hallucinations in each of the senses. Hallucinations typically occur when you perceive or interact with something not currently present.

Types of hallucinations include:

  • Auditory hallucinations (seeing things other people do not)
  • Visual hallucinations (hearing things other people do not, typically voices)
  • Olfactory hallucinations (smelling things other people do not)
  • Tactile hallucinations (feeling or sensing things other people do not)
  • Gustatory hallucinations (tasting things other people do not)
Hallucinogen addiction: Key statistics

The UN Office on Drugs and Crime’s 2019 World Drug Report highlighted a rising trend in seizures of hallucinogenic substances worldwide.
A Global Drug Survey identified psychedelics among the top 20 most commonly used drugs, constituting 6 of them.

This trend of increasing hallucinogen use, unfortunately, also indicates a paired increase in the need for treatment for either short-term health effects due to these substances or long-term effects, including addiction.

Are hallucinogens addictive?

Hallucinogens are perhaps the most wide-ranging family of drugs; many of the substances in the family vary vastly from one another. This means that some hallucinogenic substances have more addictive potential than others.
Hallucinogens can broadly be separated into two different categories: ‘classic hallucinogens’ and dissociative substances. So-called ‘classic’ hallucinogens (such as LSD and mushrooms) can be addictive as people desire to recreate the feeling of a psychedelic high.
Dissociative substances (including ketamine and PCP) are associated with higher addiction rates due to their dual-acting psychological and physical effects.

How serious are addictions to hallucinogens?

The severity of addiction to any substance depends on a range of factors, including:

  • the age you were when you began to use
  • duration of use
  • frequency you have been using for
  • the strength and amount of a substance you use
  • your metabolism
  • if you take drugs in the context of polydrug use
  • your general physical and mental health

Addiction to hallucinogens can cause a range of unpleasant long-term health effects outside of addiction.
These include the development:

  • of persistent psychosis
  • ‘the special K constellation,’
  • chronic cognitive deficits
  • long-term dips in mood
  • hallucinogen persisting perception disorder (HPPD)
  • weight loss

Signs of hallucinogen addiction

Whilst addiction can be difficult to spot, there are often signs that it is present; we need to know what to look for. Addiction can catalyse a range of ill effects and symptoms that could be misinterpreted as signs of depression, anxiety, grief, or a physical health condition.

However, if you experience any of the following symptoms alongside sustained drug use, then it is likely that you are dealing with addiction:

  • social withdrawal and isolation
  • having sore eyes and frequent headaches
  • experiencing aches and pains more than usual
  • increased tendency to become ill
  • changes to appetite (and subsequent weight loss)
  • struggling to maintain the home environment
  • struggling to meet work or school demands (missing deadlines, absences, conflict with management)
  • changes to sleep schedule (and subsequent development of insomnia)
  • experiencing financial difficulties
  • engaging in criminal activity
  • appearing paranoid or frustrated when questioned
  • spending more time alone or with a new group of individuals
  • appearing to lie or becoming more deceitful
  • having bouts of intense emotion (euphoria followed by depression)
  • appearing angry or agitated
  • conflict with spouse, family or friends

Treating hallucinogen addiction

All of the above are signs of addiction. But we can also think of them as symptoms. And when there are symptoms, there are also methods of treatment.
An addiction to hallucinogenic drugs can cause unpleasant thoughts, feelings and experiences. But these do not need to continue forever. With the help of professionals, addiction can be tackled with tailored treatment.

Addiction treatment commonly include:

Treatment usually approaches addiction from two key sides: firstly, from the perspective of your physical health and wellbeing, and secondly, to address your psychological health. This treatment aims to alleviate distress in the short-term but also limit the risk of relapse in the future.

The next stage

If you’re prepared to initiate the initial phase of overcoming your hallucinogen addiction, get in touch with a hallucinogen addiction specialist or consult your general practitioner to embark on the path to recovery.

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