Mental illnesses often cause hallucinations and delusions. Both are similar but also have some significant distinctions.
So we asked experts to break down the differences between the two.
Table of Contents
- Hallucinations include distortion of the senses
- Delusions are the disorder of thoughts
- A hallucination is something perceived (seen, heard, felt, smelt) that is not actually present
- Delusions are beliefs that are not real or misunderstanding what is perceived
- Delusions are a fixed belief that a person believes to be real and that belief is unchangeable
- Hallucinations are a false perception of the senses that can oftentimes be changeable
- Hallucinations are false sensory experiences
- Delusions are distorted thoughts
- Someone who suffers from delusions is trapped within a complex, and irrational, belief system
- In contrast, hallucinations are an internal sensory experience
- An inaccurate belief about people or situations fell under the category of a delusion.
- Hallucinations happen when she heard people say things that they didn’t say and she saw things that weren’t there
- A delusion is a belief not based in reality
- A hallucination happens when one of the senses perceives something exists when it does not
Licensed Clinical Professional Counselor | Certified Mental Health Professional | Certified Fitness Trainer | Operator, Vibrant Mind Therapeutics
Hallucinations and delusions are symptoms of serious mental illness. They are similar in terms of psychiatric impairment because both include the inability to test reality.
This means a person experiencing hallucinations or delusions can not tell the difference between what is going on in his or her mind opposed from the outside world.
A person experiencing a hallucination or delusion has a different reality in some way than others who are not experiencing hallucinations or delusions. The “some way” is what differentiates hallucinations from delusions.
Hallucinations include distortion of the senses
A person experiencing hallucinations has a difference from reality in what he or she is seeing, hearing, tasting, smelling, or touching. You can visibly tell when a person is hallucinating.
They might be looking at something that is not there or carrying on a conversation with someone invisible. They are often distracted, make infrequent or no eye contact, don’t respond to questions appropriately, move in odd manners, show unusual facial expressions and emotions which are inconsistent to the situation, are scared, and/or confused.
They often appear quite odd or downright bizarre, which is understandable considering they are experiencing stimulation both inside and outside of their own minds. They are responding to something they see, hear, taste, touch, or smell, but in all actuality, those things are originating internally for them.
This is why the phrase “responding to internal stimuli” is often used in clinical documentation to describe a person who is hallucinating.
Delusions are the disorder of thoughts
Someone who is experiencing delusions, on the other hand, is not so easy to spot visually. A delusional person has a fixed idea about something that is not based on external reality, but instead their internal reality, which is impaired.
It becomes hairy to diagnose someone truly delusional because we all have our own opinions, right? Delusions are often (not always) based on religion or the government, and who knows everything there is to know about religion or the government?
Delusions are not merely opinions, but fixed ideas of reality.
They are set and consistent for the delusional person between fields. When someone makes up “stories” or outright lies, it can be easy to spot because there are often holes in the story or the story changes from time to time and audience to audience.
Lies are difficult to remember because they didn’t really happen. Lies serve the person telling them in some way.
However, delusions are to a delusional person what they truly experienced or are experiencing, so they remain consistent.
Delusions do not serve a delusional person for some alternative gain and they are usually bizarre in nature. A delusional person is typically dead set on his or her belief and often becomes obsessed.
Hallucinations and delusions both interfere with a person’s ability to function in life(without treatment) and are serious psychiatric issues.
As stated above, they are similar in the fact that they include the inability to test reality. Folks experiencing hallucinations or delusions often do not realize their reality is any different from yours or mine.
In fact, having poor insight is part of the diagnostic criteria. If you know someone experiencing hallucinations or delusions, do not challenge or confront them.
Do not add to their stress or make them feel threatened in any way. Do not make fun of them. Instead, try to reinforce a calm, quiet, supported and comfortable environment for them.
Get the help of a qualified professional. Hallucinations and delusions are symptoms of serious mental illness, but can also result from medical conditions or substance use.
For this, it is crucial for the person to be assessed by a physician especially when first exhibiting the behaviors described in this article.
Those who experience psychosis are often wildly brilliant, and with treatment can live very fulfilling lives.
Mary Davis, M.D.
Psychiatrist | Author, Patients, Patience, and the Talking Cure: A Week in the Mind of a Psychotherapist
A hallucination is something perceived (seen, heard, felt, smelt) that is not actually present
seeing people not present (visual hallucinations), hearing voices (auditory hallucinations), smelling scents or foul odors that others don’t smell (olfactory hallucinations), feeling bugs crawling on your body (when it feels like ants, we call it formications).
Delusions are beliefs that are not real or misunderstanding what is perceived
Believing that you are God; believing that the FBI is chasing you when they are not really; believing that others are following you or watching you when they are not.
Capgras syndrome is a belief that your spouse or another important person is an impostor, that he/she has been replaced by someone pretending to be the person in your life; Fregoli syndrome is a belief that two or more different people are in fact the same person in disguise.
Some delusions represent misunderstood perceptions: seeing shadows and interpreting them as people, for instance, instead of perhaps the shadow of a tree.
Delusions can usually be categorized as grandiose (I can fly, I’m God); persecutory (other people are after me, trying to hurt me); erotomania (someone—usually someone important—is in love with me); somatic (an anorexic who believes she is fat when she is in fact significantly underweight). You must be sure that a delusional belief is in fact false in order to call it a delusion.
Dr. Amarish Dave
Board Certified Neurologist, Neurologist Care
Delusions and hallucinations are often confusing terms that have some similarities but important differences.
Delusions are a fixed belief that a person believes to be real and that belief is unchangeable
For example, I have seen patients with delusions who believe that they are a train operator. They are in reality a nursing home patient. However, no matter what facts may be presented, they will be firm in their delusion.
Hallucinations are a false perception of the senses that can oftentimes be changeable
The perception is often auditory or visual. I had a patient who always would hear the birthday song playing in their apartment. She would even ask the neighbors in her apartment to turn down the music. After repeated requests, she realized it was not really playing, and as such a ‘false perception’. It was changeable.
Visual hallucinations often involve people, often familiar people. For example, patients with Parkinson’s disease often have visual hallucinations of deceased family members.
They will often recognize them as deceased, yet carry on a conversation with the hallucination. They know it to be false, but for many actually, find comfort in the conversation.
Vicky Woodruff LMSW, MSW
Licensed Social Worker | Founder, Woodruff Counseling
Hallucinations and delusions can be a challenging part of a number of conditions most commonly in bipolar and schizophrenia-related disorders. Hallucinations and delusions although lumped together are very different.
Hallucinations are false sensory experiences
What that means is that someone may see something that is not really there or hear something that is not present. Visual and auditory hallucinations are the most common types reported but any of the other senses could be affected such as touch, taste, or smell.
With hallucinations, people can sometimes identify that it is not really on their own.
I had a patient once who reported he kept seeing glitter fall from the sky. He was aware that this was not possible and recognized it as a hallucination.
Other times individuals may need reassuring that the hallucination is false and they are okay. This can be especially true when hearing or seeing something threatening.
Delusions are distorted thoughts
Delusions are very different from hallucinations. One of my clients reported that she had been kidnapped and a piece of her brain was taken and replaced with an evil brain. She believed this to be true.
In the case of delusions, confronting the patient with reality and attempting to logically dismiss the delusion can make the individual more agitated and upset.
You can not argue with a delusion because it so deeply rooted in the individuals thought process it can’t be challenged.
You also do not want to encourage or provoke the delusion. The key here for family, friends, and providers is to take a stance on neither confirming or denying.
I told my patient that what she reported sounded frightening that I was here to support her and we would figure a way forward together. Never did I confirm that the reported situation was happening instead I validated how she was feeling and promised to help.
Delusions and hallucinations do not go away with talk therapy alone. An antipsychotic will likely be prescribed to help reduce symptoms. In the meantime, remember to support and validate the individual. It can be scary and overwhelming but this is something that you will get through.
Psychotherapist | Registered Associate Marriage & Family Therapist
People often confuse delusions with hallucinations, but they are actually two very different phenomena.
Someone who suffers from delusions is trapped within a complex, and irrational, belief system
For example, someone might believe that they are being spied on by aliens. The aliens can read their mind, and are controlling the world around them. In this case, the person will constantly find evidence in their daily life that, to them, confirm the fact that aliens are in control. Because the belief system is so complete, you can’t talk someone out of a delusion or convince them that they’re wrong.
In contrast, hallucinations are an internal sensory experience
Auditory hallucinations are the most common type of hallucination. A person who suffers from auditory hallucinations will most commonly hear a voice, or voices, talking to them.
The voice may tell them to take certain actions or give a running commentary on what’s going on around them. These voices are often negative or hostile. There are other types of hallucinations, visual and olfactory (smell) are the two most common.
It’s not uncommon for someone who is delusional to also have hallucinations. But, they are two separate and very different experiences.
Laura Vaillancourt, MA, LMHC, GMHS
Licensed Mental Health Counselor | Mental Health Specialist | Geriatric Care Consultant, Eldercare Counseling
I often see these terms confused in my work with families as an eldercare coach and counselor. Many people with memory impairment have these symptoms written off as “part of dementia”.
It is important to know the difference because a change in condition as evidenced by having hallucinations or delusions can be a sign of something more serious, such as delirium caused by an untreated infection or negative reaction from medication.
While types of dementia can cause delusions (the belief that something has occurred), it is rarer for hallucinations to occur (seeing or hearing something at the moment).
It is important to make the distinction between if the person is actually seeing or hearing something at the moment (hallucination), or saying they saw or heard something in the past (a delusion).
Speaker | Mental Health Volunteer | Author, Broken Brain, Fortified Faith: Lessons of Hope Through a Child’s Mental Illness
I’m a mom who walked beside my adult child as she experienced both delusions and hallucinations.
An inaccurate belief about people or situations fell under the category of a delusion.
She believed people were tampering with her life, such as her bank account, going through her things, and tampering with her car. There was no foundation for these things, but her mind convinced her they were happening.
Eventually, her delusion included a conspiracy against her life. She perceived newspaper articles, television programs, and movies were all written about her life. That’s a delusion.
Hallucinations happen when she heard people say things that they didn’t say and she saw things that weren’t there
They were as real to her as seeing a typed word on a page or hearing a podcast is to me. Delusions and hallucinations are frightening and upsetting to the person experiencing them.
Compassion and understanding are important qualities to learn and use when a loved one suffers from either or both. Our daughter found help, accepted treatment, and no longer has them.
Michael J. Brown, RPh, BCPS, BCPP
Consultant Pharmacist, Sunshine Nutraceuticals
A delusion is a belief not based in reality
A delusional person may believe they are influential, powerful or related to a famous person when, in fact, they are not.
I have met patients who believed they had a direct connection with God and have been sent to convey an important message usually regarding the end of the world. Others were convinced the President of the United States was down the hall and nuclear war had started.
These people may also think they are living in a past or future time. They may believe they are much younger than they are and depend on their parents for their care.
In these cases, the parents have often been deceased for many years. Alternatively, they may think their children are still babies when they are full-grown adults.
A hallucination happens when one of the senses perceives something exists when it does not
Hallucinations are often auditory. The person hears voices inside their head, telling them to do something or criticizing them. These voices tell them they are worthless or shouldn’t eat because the food is poisonous. The voices often tell them not to listen to others who are talking to them.
Visual hallucinations happen when a person sees an image that doesn’t exist. These images may be pleasant or frightening. They may be images of children, animals, satan, or monsters.
I have often had patients tell me someone was in the room with us during an interview. They will say “Can’t you see her, she is standing right over there by the door”. Another common visual hallucination is when a person can see music.
Tactile hallucinations happen when a person feels something that isn’t there. The classic example is the feeling of bugs crawling on the body. Patients have told me they could feel people pushing or hitting them. Others have described the sensation of water pouring over their head.
An olfactory hallucination is a smell perceived by the person that isn’t present. These smells can be pleasant or unpleasant. The person may smell apple pie or smoke.
I have observed patients who have more than one type of hallucination happening concurrently. An example would be a person kneeling and petting a dog. They are convinced the dog is there and can feel the fur as they pet it when in reality no dog exists.
Certified Mental Health Consultant, Enlightened Reality | Family Care Specialist, Maple Holistics
Both hallucinations and delusions are symptoms of psychosis but they’re not the same thing. The biggest difference between hallucinations and delusions lies in how the two are experienced.
Hallucinations involve the senses. What you’re experiencing isn’t real, but you might ‘feel’ it in some way.
Delusions are beliefs that aren’t real or based on reality. Despite being shown evidence to the contrary, people who are delusional stay firm to their beliefs.