Side Effects of Hypnosis: What Actually Happens

Most people feel fine. Some feel groggy, a few get a mild headache. Serious problems are close to unrecorded, and the numbers are further down.

My assistant greeted her warmly and handed her a clipboard and a black pen. The questions were easy. Sheryl paused as she saw the question: Have you ever been hypnotized before?

Three years ago Sheryl had been at the fair. Third row, a Diet Dr Pepper in one hand, sharing a pulled pork sandwich with her husband. Becca volunteered. Sheryl didn't know that Becca could moonwalk. Heck, Becca interpreted the demands of the people of Jupiter in their native tongue.

She laughed until her eyes watered.

She wrote "No."

Not me. But Becca sure had been.

She could answer every question on that page honestly. The one she was afraid of wasn't on the form. Nobody puts it on a form. It was the thing with her husband, she was not here for that, and she did not want to go there.

If you are wondering whether hypnosis is safe, you're in the right place.

You want help with something. And you probably have a few questions, even something you'd feel a little silly saying out loud. Something about control. About what you might say once you're in that chair.

That's not a silly question. And I am here to give you the best answers I can.

I've been doing hypnosis since 2008. I've done more than twenty thousand one-on-one sessions.

Hypnosis isn't about control. It's about cooperation. Working together toward a common goal.

My job is to help you with what you came in for. You don't have to tell me anything you aren't ready to say.

1. How this page is written

Over explaining side effects creates side effects.

That has a name. The nocebo effect. Tell someone what might go wrong, and they are more likely to get it. ^[1]

This is not imagination. It has been measured in the body, not just in what people report.

There is a twist. How a thing is said may matter more than what is said. A warm, unhurried explanation seems to do less harm than a cold one carrying the same facts.

One more finding, and it is why this page opens the way it does. Most warnings lead with the small number of people who have a problem. Almost nobody leads with the large number who are fine. ^[1]

So a page like this one has a problem built into it. Hand somebody a list of frightening things and it can affect what happens to them.

Here is how I am handling that.

I am going to tell you what happens during a session, how often it happens, and what usually causes it. Not a list of symptoms to check yourself against. A cause you can understand, and usually prevent.

My hope is to help you have the best experience you can have.

One more thing before you read on. If you have already had a session, you may want to read what to expect after hypnosis.

2. What are the side effects of hypnosis?

Most people walk out feeling fine.

Some feel groggy for a few minutes. Some get a mild headache. Some feel more emotional than they expected for an hour or two.

Serious problems are close to unrecorded. I will show you numbers further down the page.

One thing worth knowing: reading a list of side effects makes some people more likely to have them.

Here is what we will look at.

What people report	How often	How long	What usually causes it
Drowsiness or grogginess	The most common one	Minutes to about an hour	Not taking enough time coming back from hypnosis
Mild headache	Second most common	Under an hour	Eye strain, head position
Light-headedness	Less common	Minutes	Breathing pattern during the induction
Feeling emotional	Common after emotional work	Hours to a day	The work itself, not the hypnosis
Vivid dreams that night	Occasional	One night	No studies

Grogginess is usually about how the session ended. A headache is usually about your eyes or your neck.

Neither one is hypnosis doing something to you.

3. Is hypnosis dangerous?

For most people, no.

Most practitioners will tell you that side effects are rare and mild.

Most don't tell you how rare.

That is not laziness. It is that most of the research hasn't looked.

A review in 2024 went through forty-nine meta-analyses of hypnosis. Twenty-eight of them contain no safety information at all. ^[2]

Here is what the research shows.

Across hypnosis studies listed on ClinicalTrials.gov, serious side effects linked to hypnosis came out at zero. ^[3]

Other side effects came out at under half a percent. That review covered medical uses of hypnosis only.

In eight studies of hypnosis for irritable bowel syndrome, only one person out of 238 left the study because of an adverse event. That one person had a panic attack. ^[4]

When researchers ask people about their experience right after hypnosis, the picture changes some. Anywhere from eight percent to forty-four percent report temporary side effects when asked. ^[5]

Wait for someone to complain and you get a small number. Ask people directly and you get a larger number.

Researchers disagree about this in print. One who has run hypnosis research for decades puts the rate under five percent. ^[17] Another, who reviewed the laboratory work, puts it far higher.

They are both looking at real data. They are measuring different things.

So here is my honest reading. Most side effects are common, minor, and short-lived.

That is not the same as saying nothing ever happens. Here is the honest list.

Minor after-effects.

Grogginess, a mild headache, feeling more emotional than you expected for an hour or two. Common, short-lived, and usually caused by something ordinary. The causes are a couple of sections down.

False memories, not from hypnosis by itself — from a specific kind of memory work. There is a section on it further down.

A short list of conditions to ask your doctor about first.

I am not a physician and I do not diagnose anything. The list is further down, along with how much the reasoning behind it is worth.

Driving before your head is clear.

Take a few more minutes. That one is at the end of the page.

If something on that list is the reason you are hesitating, tell me about it in a 15-minute consultation.

4. What does hypnosis actually feel like?

People tell me that hypnosis feels familiar. Normal. That usually surprises people.

Almost everybody arrives expecting to feel gone. Asleep, "knocked out," blank, or floating somewhere, with the hour disappearing. That expectation comes from stage shows and movies, and from the way a lot of the field talks about "going under."

Some people do lose track of time. Not everyone does.

Most of what you will read calls hypnosis relaxation. Plenty of people do feel relaxed, and that is fine. But relaxation is a side effect from hypnosis, which doesn't always show up.

Hypnosis relies on focused attention. Your attention narrows. Your mind responds more readily to a suggestion.

During hypnosis, you are awake. You hear everything. You remember most of it.

You aren't under anything. Not a spell, not mind control.

The American Psychological Association's defines hypnosis this way. Hypnosis is focused attention and reduced peripheral awareness, with an enhanced capacity to respond to suggestion. ^[12]

Doug came to me for help with a fear of speaking in public. In his first session, he sat with his eyes closed for about thirty minutes. He heard a truck go by outside, thought about an email he needed to send, and remembered most of what I said. He was also hypnotized the whole time.

After his third session he told me something was different. He had thought about the staff meeting on Tuesday and had not felt his stomach drop. That was new.

That is what hypnosis usually looks like. Ordinary in the chair. Different afterward.

The emotions you feel in hypnosis depend on what you are there to work through. Hypnosis itself does not produce emotion. It is the goal you are pursuing, or the technique we choose, that might tap into one.

Think about the gap between where you are now and where you want to be. Notice what emotions come up. Fear, anger, sadness, guilt, shame, overwhelm are common emotions. But everyone is different. Not all the emotions you already have will necessarily show up during hypnosis. But the ones that are already there are the ones that might come up.

Some people cry in a session. It does not mean something went wrong, and it does not necessarily mean we stop.

When I see tears I ask what kind of tears they are. Some tears come from something letting go. Some come from distress, which is a different thing. I handle distress differently.

Nobody has studied crying in hypnosis at all. These are my own observations.

My advice is to leave your expectations of what hypnosis will be like at the door. After a few sessions you will have a better idea about how you respond. Give yourself permission to enjoy your session.

That assumes you have one booked. If you don't, start with a 15-minute consultation.

5. Why do I feel groggy afterward?

Honestly, I couldn't find any scientific commentary to explain it. Here are my observations, and what to do about it.

Often people don't give themselves enough time to come out of hypnosis. Take enough time after your session to get your wits about you. From experience, most people are ready to get back at life after three to five minutes. If you are not feeling with it, take another fifteen before you drive.

Sometimes hypnosis students don't help clients return from hypnosis properly. Clients often feel tired, foggy, and disoriented when students skip this step. ^[7]

I am not saying slowing down will necessarily end your drowsiness. People have tried to prevent it on purpose, but with mixed results.

In one small study, fourteen people had hypnosis explained to them first. Afterward, they did a stretching exercise. Fewer of them felt drowsy, but the difference was too small to rule out chance. ^[14] Another study found that safeguards reduced the longer-lasting effects. But the measures had no impact on short-term effects. ^[15]

Grogginess usually doesn't last that long, and it may not be related to hypnosis alone.

You sat still with your eyes closed for forty minutes. Some people doze. Contact lenses can dry out. Necks sometimes stiffen in one position.

You walk out of a movie after two and a half hours. In the lobby, the lights are too bright. The sound is too loud. There's a moment to adjust. Nothing is wrong with you. It's part of leaving the theater.

What I do is invite people to take their time coming back. Then I watch clients take their first few steps across the room. It seems to help.

If you ever leave an office foggy, say so. And give yourself permission to sit down for a few minutes until you feel ready to go.

6. Can I get stuck? Can I be made to do or say something against my will?

Both questions come from a similar deeper worry. Does hypnosis give control to somebody else? And the short answer is no, it does not.

Nobody stays hypnotized. There is no case in the medical literature of a person who could not be brought out. The literature often talks about people from stage shows, not clinical work. The cases describe stage participants who took longer than expected in coming back. ^[16]

Now the second question.

The APA definition earlier is precise about it. Hypnosis creates an enhanced capacity to respond to suggestion. A capacity to respond is not obedience. A suggestion still has to land on somebody willing to take it.

You keep your values in hypnosis. You keep your judgment about what you will and will not do. A good hypnotist helps boost your existing values. They guide you toward your own goals.

The same goes for what you talk about. You decide what you say in hypnosis, the same as you do in any conversation. I ask. You choose your answer.

Sometimes people are picturing a stage show when they ask this question. That is a fair thing to wonder about, and there is a section on it further down.

Here is the part people don't consider. Almost everyone who calls me has already lost control of something. A craving that fires before they decide. A habit that runs itself. A fear that arrives before they have spoken a word. That is why they picked up the phone. The work is about giving you back control, not taking it away.

If that is the part you are weighing, bring it to a 15-minute consultation.

7. Can hypnosis create false memories?

Yes, in one specific situation — when someone goes looking for a memory you do not already have.

It is not unique to hypnosis. Ordinary questioning does the same thing. What hypnosis adds is certainty.

Vince is sitting in the big blue recliner in my office. A light sheen of sweat is on his hands before he wipes his palms on his work jeans. He really needs answers. He yells too much. Like a firecracker waiting for a lighter.

"Something must have happened to me to make me so angry," he says. "The problem is I have had a good life. I don't remember anything bad. But something has to explain why I am this way. You gotta help me figure out what went wrong."

"It sounds like you want answers," I say. Vince nods vigorously.

"Here is the question you need to ask yourself. Do you want to solve the mystery of 'why' or do you want to stop being so angry all the time?

"Here is what I can do. I can help someone work towards a goal. Here is what no one can do: tell you what caused your problem when no cause is apparent."

If you are not sure whether your goal is something I can work with, ask me in a 15-minute consultation.

What the research says about what Vince was asking for

A hypnotized person becomes more open to suggestion. When a gap shows up in a memory, the mind fills it in so the answer feels whole.

The danger is not mainly that hypnosis invents things. It is that it makes you more certain about what shows up in your mind: real or imagined.

Now the number that puts it in proportion.

When researchers try to create false memories, about three people in ten end up with one. ^[9]

No hypnosis is involved in those studies at all. Just ordinary suggestions, done by ordinary people asking questions.

As I write this, there is still an open debate about the result. A reanalysis put it closer to four percent. The original authors pushed back.

Whatever the real number is, the risk is not unique to hypnosis. Three things seem to cause it.

A leading question.

Guided imagery of a specific suggested event.

Any attempt to retrieve a memory somebody does not already have.

One study put hypnosis and leading questions head to head. Both increased memory errors. Leading questions created more errors than hypnosis. The two together increased the risk. ^[10]

The US Supreme Court described how this works in a ruling: the person "experiences 'memory hardening,' which gives him great confidence in both true and false memories." ^[8]

The risk is specific. False memories can occur when a therapist suggests you experienced an event you don't recall.

Two people, two different things

Sammie knows exactly when her fear of flying started. A rough descent into Denver, eight years ago, the overhead bins rattling the whole way down. She has not been comfortable on a plane since.

She is not asking me to find a memory. She already knows what it is.

That is common work and I do it all the time. There are good ways to change what an old event does to somebody today.

Kip is a different situation. His therapist sent him to find evidence of something specific in his past. Now Kip is worried that something bad might have happened to him. Before therapy, that worry never crossed his mind.

Here is what I told Kip.

"What I can tell is that you are worried and afraid of what you might find. I don't do this kind of memory retrieval work, and here is why.

"Nobody knows whether there is anything to find. Not your therapist. Not you. Not me.

"So we would be starting from a guess. And a mind will answer almost any question you ask it. That is what minds do. Something would probably turn up. Neither of us would have any way to know whether it was true.

"Now think about who sent you. Somebody you trust has already told you there may be something back there. And you want to do this right. Combine that with hypnosis and you have everything you need to build a false memory.

"What you imagine might get stuck in your head. You might decide to act on it. You might say something to somebody in your family that cannot be unsaid. And it could rest on something you invented in a suggestible state.

"So I recommend we do not look.

"Here is what I would do. Go back and tell her what I said. She may have a reason I have not heard, and I am glad to talk to her about it if you want me to.

"And if there is something in your life right now you want help with, I may be able to help you. I do not need to know where it started to help."

Kip sat back a little in the chair.

Part of him had been dreading the search.

That was not a hard call. Looking for a memory when nobody knows there is one is a bad idea, whoever is asking.

The British Psychological Society said it best, and said it in 2001. "Hypnosis should not be used on the assumption that it can recover memories of events of which the client has no recollection but which are the cause of his or her presenting problems." ^[11]

8. Who should be careful, and why?

First, plainly: I am not a physician and I am not a licensed mental health provider. I do not diagnose anything and I do not treat conditions. If any of what follows applies to you, the person to ask is your doctor. Here is the list:

Psychosis, schizophrenia, marked paranoia, or severe dissociation. Every list in the field names these as reasons to avoid hypnosis. Experts worry about a person becoming less stable. In these conditions, hypnosis is an unknown, not properly researched.

Epilepsy is on the NHS list with no reason given, and I am not going to tell you their caution is wrong. I am not a neurologist. So if you have a seizure disorder, ask your doctor before starting. Paced breathing is worth asking about specifically.

When I wrote this article, the organizations that publish these lists have not published the reasons for their warnings. The NHS names two conditions and cites nothing. ^[18]

9. Is stage hypnosis the same thing? What about apps?

Stage hypnosis is real hypnosis pointed at a different job.

A stage hypnotist chooses the most responsive people from a big crowd. Everyone in the room is there to be entertained. The goal is a good show. Nobody is working on anything.

A UK government review looked at stage hypnosis specifically. The British Psychological Society and the Royal College of Psychiatrists nominated a panel. It found "no evidence of serious risk to participants in stage hypnosis, and that any risk which does exist is much less significant than that involved in many other activities." ^[13]

So it is not usually dangerous. More importantly, nothing like stage hypnosis happens in my office.

Apps and recordings can be useful. What they do not do is tailor suggestion. Imagine a weight loss recording that spends 30 minutes telling you not to eat sugar at night. But you don't do that anyway. It may not hurt you, and it is not likely to help either.

Some intermediate and advanced hypnosis techniques require feedback from clients. This feedback can be verbal or nonverbal. Recordings and apps cannot respond to client feedback.

10. What should I do if I feel off afterward?

The first rule is to tell your hypnotist. A good one will want to know something has happened.

In a study of 100 therapists using regular talk therapy, 43 of their patients had side effects. Most therapists didn't notice problems. Then, a researcher asked about side effects. ^[6]

That is not about hypnosis. It is about how easily any practitioner can miss a side effect.

And I can't help something I don't know about.

Also, don't drive off right away if your head is not clear. If you feel off, give yourself fifteen minutes. Walk around the block.

Feeling emotional after emotional work can happen. Usually that will pass in a few hours.

I wrote a longer page about how long most side effects last.

If you are ever in life-threatening distress, call emergency services. There may be something beyond hypnosis happening.

11. Before you book

Before you book, write down the questions you have. It is better to ask your most important questions. Even the one that embarrasses you a little to ask.

When you have your list, book a 15-minute consultation and bring it.

12. Questions people ask

Is hypnosis safe?

For most people, yes. Serious problems are close to unrecorded. Minor, short-lived ones are common. The people who should check with a doctor first are listed above.

How long do the effects last?

Grogginess usually clears in minutes. A headache usually clears within the hour. Feeling emotional after emotional work can last into the next day.

Will I remember everything?

You will likely remember most of it, the same way you remember most of any conversation. You are aware the whole time.

Can hypnosis cause memory loss?

No. Hypnosis doesn't erase memories. Some people lose track of time during a session, which is a different thing.

Is hypnotherapy different from hypnosis?

Hypnosis is focused attention. Hypnotherapy uses hypnosis to work towards a worthwhile goal. This page will answer common questions about both.

Are the side effects different with an app or a recording?

Nobody has studied it, so I cannot tell you. What I can tell you is that a recording cannot notice and can't help if you do have a side effect.

How many sessions will I need?

It depends on the person and the goal. That is exactly what the 15-minute consultation is for.

13. About this page

Written by William Wood, hypnotherapist, Northern Utah Hypnosis Center, Ogden, Utah. Working with clients since 2008.

Trained through HMI, AHA, NGH and ABNLP. Completed ABNLP Master Practitioner certification. NLP Trainer, certified by NLPCA, and has trained NLP nationally and internationally alongside Tim Hallbom. Trained through the International Medical and Dental Hypnotherapy Association. Contributing author to the IMDHA's journal, Unlimited Human, for over ten years.

I am not a physician and I am not a licensed mental health provider. I do not diagnose or treat conditions.

Every figure on this page names its source. Where nobody has counted, the page says that too. Last reviewed September 18, 2026.

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Notes and sources

1. Grosso, Barbiani, Cavalera, Volpato & Pagnini (2024). Risk factors associated with nocebo effects: a review of reviews. Brain, Behavior, & Immunity — Health 38, 100800. Open access. A review of 43 earlier reviews; read in full Sep 17, 2026. WHERE THE EVIDENCE COMES FROM, and it matters: the nocebo effect is best documented in pain research, not in hypnosis. In that work, telling someone to expect more pain produces more pain, and proglumide — a drug that blocks cholecystokinin receptors — blocks the increase (Benedetti et al. 2005, post-operative patients given a saline infusion). That is the basis for saying the symptoms are measurable in the body rather than only in what people report. No comparable mechanism work has been done on hypnosis. Also from this review: negatively framed information raises side-effect expectations; clinicians typically state the small percentage who have a problem rather than the large percentage who do not; and the reviewers note a clinician's manner "might be a more pertinent risk factor for nocebo effects than the actual content of the information provided" — stated as a possibility, not a finding. Do not harden it. REPLACES Coe, Peterson & Gwynn (1995), AJCH 38(1), 3–12, cited here until Sep 17: that paper's own follow-up study failed to replicate its result, its first study showed an unexplained ordering between groups, and its title is "initial findings."
2. Rosendahl, Alldredge & Haddenhorst (2024). Frontiers in Psychology 14:1330238.
3. Bollinger (2018). The rate of adverse events related to hypnosis during clinical trials. American Journal of Clinical Hypnosis 60(4), 357–366. Medical conditions and procedures only.
4. Schaefert, Klose, Moser & Häuser (2014). Psychosomatic Medicine 76(5), 389–398.
5. Gruzelier (2000). Unwanted effects of hypnosis. Contemporary Hypnosis 17(4), 163–193. Laboratory volunteers, not clients. Gruzelier's own reading: in the laboratory these "may be regarded as no more than a trivial nuisance for most participants." He immediately adds that a health setting is different — a headache that is a passing discomfort in an experiment can be enough to put a patient off practising self-hypnosis at home. Both halves travel together.
6. Schermuly-Haupt, Linden & Rush (2018). Unwanted events and side effects in cognitive behavior therapy.
7. Kluft (2012). American Journal of Clinical Hypnosis, vols 54–55. Studied in training settings.
8. Rock v. Arkansas, 483 U.S. 44 (1987), at 59–60.
9. Scoboria et al. (2017). Memory 25(2), 146–163. No hypnosis involved.
10. Scoboria, Mazzoni, Kirsch & Milling (2002). Journal of Experimental Psychology: Applied 8(1), 26–32.
11. British Psychological Society (2001). The Nature of Hypnosis. Leicester: BPS.
12. Elkins, Barabasz, Council & Spiegel (2015). APA Division 30 revised definition of hypnosis.
13. Home Office Circular 39/1996 (UK). Review of stage hypnosis.
14. Crawford, Hilgard & Macdonald (1982). Transient experiences following hypnotic testing and special termination procedures. International Journal of Clinical and Experimental Hypnosis 30(2), 117–126. Very small sample: 5 with the intervention, 9 controls. Verified Sep 16, 2026 against Crossref and PubMed (PMID 7085134). The finding is reported here as summarised in Gruzelier (2000), note 5 — the 1982 paper itself was not read directly.
15. Page & Handley (1993). American Journal of Clinical Hypnosis 36(1), 26–37. Safeguards reduced longer-term after-effects from 19.7% to 13.8% (p=.04) and had no effect on short-term after-effects.
16. Kleinhauz et al. (1979), International Journal of Clinical and Experimental Hypnosis 27(3), 219–226; Crawford et al. (1992), Journal of Abnormal Psychology 101(4), 663–667; Wain & Dailey (2010), American Journal of Clinical Hypnosis 52(3), 183–188. Difficulty re-alerting is documented; nearly every case is from stage hypnosis, not clinical work.
17. Kihlstrom, J.F. Hypnosis human subjects protocol, University of California, Berkeley, updated April 2001. Adverse effects "occur in less than 5% of individuals who ... participate in hypnosis research (in our laboratory, they occur in less than 1% of subjects)," and are "transitory, and easily resolved." Refers to drowsiness and mild headache in research participants. A university human-subjects protocol, not a peer-reviewed paper — say so if the sentence ever leans harder on it.
18. NHS, "Hypnotherapy," nhs.uk. Page last reviewed 1 May 2026. Names two conditions — "you have schizophrenia or a history of psychosis" and "you have epilepsy" — under "Hypnotherapy may not be safe for you if." Gives no reason, evidence or citation for either. Verified Sep 16, 2026. This note sources a claim about an absence, so re-check the date before any future review.

Disclaimer

Individual results vary. Hypnosis and hypnotherapy are not meant to diagnose or treat any disease; they are intended to provide information, education, and motivation to support you in making positive changes in your own life. The clients described on this page are composites drawn from real consultations over many years. Identifying details have been changed and combined so that nobody is identifiable. None of them represents a specific individual or guarantees a particular outcome.

Written by William Wood · Northern Utah Hypnosis Center