Hallucinogens

Overview

Hallucinogens are a group of substances that change how a person senses the world. They can make someone see, hear, or feel things that are not there (these are called hallucinations), blur the line between what is real and what is imagined, and make time feel like it is speeding up or slowing down. Some come from plants and fungi that grow in the wild. Others are made in laboratories. People usually swallow them, and the effects can last from a few hours to a day or more. The experience is often called a 'trip', and it can be pleasant or very frightening. Because the effect is so strongly linked to a person's mood, surroundings, and health at the time, the same substance can feel completely different from one occasion to the next.

Surveys in many countries suggest that a noticeable minority of adults — often around one in ten or more in some age groups — have tried a hallucinogen at least once. Most of this use happens in the late teens and twenties. Using regularly over a long period is much less common than trying once or twice.

Anyone can be affected, but use is most common among young adults and students. Some people are at higher risk of a bad reaction: those with a personal or family history of psychosis or schizophrenia, people with anxiety or depression, people who use alone or in unfamiliar places, and people who mix substances. Children can be accidentally affected by eating wild plants, mushrooms, or fungi, which is a medical emergency.

Symptoms

Common symptoms

• Seeing, hearing, or sensing things that others do not see or hear
• Colours looking brighter, objects seeming to move, breathe, or change shape
• A distorted sense of time — minutes feeling like hours, or hours passing in a blur
• Feeling detached from your body, or like you are watching yourself from outside
• Strong mood swings — sudden laughter, tearfulness, fear, or a sense of deep meaning
• Confused or jumbled thinking, and trouble telling what is real
• Enlarged (widened) pupils, sweating, a faster heartbeat, dry mouth, shakiness
• Feeling dizzy, light-headed, or sick to the stomach
• Numbness or tingling, and changes in how things feel to the touch
• Poor judgement about danger — for example, walking into traffic or trying to fly

Symptoms in children

• Young children may not be able to explain what is happening, so watch for behaviour changes instead
• Sudden confusion, sleepiness, or being unusually hard to wake
• Agitation, crying that cannot be comforted, or staring blankly
• Unsteady walking, clumsiness, or floppiness
• Vomiting, drooling, or a fast heartbeat
• Any child who may have eaten a wild plant, mushroom, or fungus should be checked by a doctor straight away

Symptoms in older adults

• Confusion or hallucinations that come on suddenly — this should always be checked, as it can have many causes
• Unsteadiness and a higher risk of falls and fractures
• Hallucination-like side effects from prescribed medicines, especially when several are taken together
• Interaction between recreational substances and medicines for the heart, blood pressure, or mood
• Symptoms being mistaken for dementia or delirium, when the real cause is different

Causes

Main causes

• Recreational or experimental use — often out of curiosity, for fun, or because friends are using
• Use at parties, festivals, or in settings where people feel pressure to join in
• Accidental exposure — eating wild plants, mushrooms, or fungi that contain these substances
• Side effects of some prescribed medicines, or interactions between several medicines
• Other medical conditions that can cause hallucinations (such as fever, infection, or a mental health condition) — this is why a proper check-up matters

Risk factors

• Being in your late teens or twenties
• A personal or family history of psychosis, schizophrenia, or bipolar disorder
• Current anxiety, depression, or a history of trauma
• Using alone, or in an unfamiliar or unsafe place
• Taking a larger amount than usual, or a substance of unknown strength or purity
• Mixing with alcohol or other drugs
• Feeling low, stressed, or frightened before using — mood strongly shapes the experience
• Having a heart condition or taking medicines that affect the heart

When to see a doctor

See a doctor urgently if:

• Any of the emergency signs listed above — call your local emergency number first
• Ongoing confusion, panic, or unusual perceptions after the effects should have worn off
• You feel you cannot stop using, or using is causing problems at home, work, or school
• You have hurt yourself or someone else, or you have been in a risky situation
• You are pregnant or think you might be, and you have used

Book a routine appointment if:

• You would like honest, non-judgemental information about a substance
• You are worried about a friend or family member's use
• You have noticed changes in mood, sleep, or memory that you want to talk through
• You want to talk about your mental health or your risk of a bad reaction
• You are taking prescribed medicines and want to know about possible side effects

Diagnosis

There is no single test for hallucinogen use. A doctor or nurse will usually start with a calm, private conversation: what was taken, how much, when, whether anything else was used, and how you are feeling now. They will check your heart rate, blood pressure, temperature, breathing, and pupils, and look for any injuries. They will also ask about your mood, thoughts, and any hallucinations or unusual experiences, and about your medical history and medicines. The aim is to keep you safe and to rule out other causes of hallucinations, such as infection, a head injury, or a mental health condition.

Tests that may be done

• A physical examination, including heart rate, blood pressure, temperature, and breathing
• A urine or blood test that can screen for a range of substances (a 'toxicology screen')
• Blood tests to check sugar levels, salt balance, kidney and liver function, and to look for infection
• An ECG (a tracing of the heart) if there are heart symptoms or a heart condition
• A mental health assessment — a structured conversation about mood, thoughts, and safety
• Imaging such as a scan, only if there has been a head injury or other specific concern

What to expect at your appointment

Most people are seen quickly, kept in a quiet and safe space, and monitored while the effects wear off. You may be asked to stay for a few hours. Staff will explain what they are doing and will treat what they find. You will not be in trouble — confidentiality is respected, and the priority is your safety and your health. If follow-up is needed, you may be referred to a drug and alcohol service or to mental health support.

Treatment

Most of the time, the main treatment is calm, safe supportive care while the effects pass. The person is kept in a quiet, low-stimulation space with someone they trust, given fluids, and watched for any danger signs. Most bad reactions settle within hours. When use is causing ongoing problems, treatment focuses on understanding why it is happening and building skills and support to change it — with no blame and no lectures.

Self-care at home

• Tell someone you trust where you are and how you are feeling
• Stay in a safe, familiar place with soft lighting and low noise, and avoid driving, swimming, heights, or machinery
• Sip water and rest — do not take more of anything to 'fix' how you feel
• Write down what happened afterwards, including what helped, so you can spot patterns
• Plan ahead: decide in advance how you will get home and who you will call
• Build a regular routine around sleep, meals, and gentle activity — these steady your mood
• Learn to recognise early warning signs in yourself, such as low mood or rising anxiety, and reach out early
• Keep a list of your medicines and share it with any doctor or pharmacist you see

Medical treatments

There is no specific antidote that reverses a hallucinogen. Medical care is supportive: a safe environment, close monitoring, fluids, cooling if the body overheats, and treating any injury. Doctors may use calming medicines for a short time if someone is extremely agitated, very frightened, or a danger to themselves — this is always a clinical decision made by the treating team. If someone has repeated distressing 'flashbacks' or ongoing anxiety or psychosis, they may be referred to mental health services for assessment and talking therapy. Where use is problematic, treatment usually involves talking therapies such as cognitive behavioural therapy (a structured way of changing unhelpful thought and behaviour patterns) and motivational work, plus practical support from a drug and alcohol service. Peer support groups can be a valuable addition. Any treatment plan should be tailored to the person and reviewed regularly.

Living with this condition

Life after a difficult experience with hallucinogens can feel unsettling for a while. Some people notice fleeting visual changes, anxiety, or poor sleep that lasts days or weeks. These usually settle, but they are much easier to cope with when you tell someone and get support early. If you are trying to cut down or stop, take it one day at a time, avoid the people and places linked to using where you can, and fill the space with things that matter to you — sport, study, work, music, or time with people who support you.

Lifestyle tips

• Keep a steady sleep routine — sleep is one of the strongest protectors of mental health
• Spend time with people who support you and who do not pressure you
• Have a plan for nights out: who you are with, how you are getting home, and what you will say if offered something
• Learn a simple way to say no, and practise it out loud so it feels natural
• Limit alcohol, as it lowers your guard and increases the chance of mixing substances
• Keep a diary of mood, sleep, and any unusual experiences so you can see progress and spot early warning signs
• Book a routine check-up with your doctor if you have any ongoing concerns

Diet and exercise

Eating regular meals, drinking enough water, and moving your body most days all help to steady mood, sleep, and thinking. You do not need a strict plan — a daily walk, cycling, swimming, or a class you enjoy is enough. Gentle exercise is also a good way to manage the restless, anxious energy that can follow a frightening experience. If appetite or sleep has been poor for more than a couple of weeks, mention it to your doctor.

Mental health and emotional wellbeing

A bad experience can leave people feeling shaken, anxious, or low, and sometimes frightened by their own thoughts. Recurring visual changes or 'flashbacks' can be distressing and can affect work, study, and relationships. These feelings are understandable and treatable. Please do not cope alone. If at any point you have thoughts of harming yourself or ending your life, contact your local emergency number or a crisis line straight away, or go to the nearest emergency department. Crisis support is there for exactly this moment, and reaching out is the right thing to do.

Prevention

You cannot control what is in a substance or how your body will react, so the only way to remove the risk completely is not to use hallucinogens. If you or someone you know does use, harm reduction matters: never use alone, start with a very small amount, avoid mixing with alcohol or other drugs, use only in a safe familiar place with a trusted person who is not using, plan how to get home, and know the warning signs that mean calling for help. Education works best when it is honest rather than frightening — talk openly with young people about risk, consent, and looking after friends.

Screening programmes

There is no routine screening test for hallucinogen use. What does help is a regular conversation about substance use with your doctor, nurse, or pharmacist. Mental health checks are also valuable if you have a personal or family history of psychosis, or if you are noticing changes in mood or perception. If you are offered a brief questionnaire about drinking or drug use at an appointment, answering honestly helps you get the right support.

Complications

If left untreated

• Persistent psychosis (losing touch with reality) that lasts beyond the immediate effects, especially in people who are vulnerable to it
• Ongoing visual disturbances, anxiety, or 'flashbacks' that interfere with daily life
• Injuries and accidents from misjudging danger, driving, swimming, or falls
• Risky sexual behaviour, with a risk of sexually transmitted infections or unplanned pregnancy
• Worsening anxiety, depression, or sleep problems
• Problems at work, college, or home, and money or legal difficulties
• Strain on relationships with family and friends
• Using more often, or mixing with other substances, which raises the risk of serious harm

Long-term outlook

The great majority of bad reactions settle within hours to days, and most people who try hallucinogens do not go on to have lasting problems. Even for people who have had a frightening experience or a period of difficult mental health, recovery is common with the right support. The most important step is telling someone and getting help early. Many people go on to feel well again and find that the experience becomes something they understand and have moved past, rather than something that defines them.

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