Hallucinations And Delusions Are Surprisingly Common

Illustration for article titled Hallucinations And Delusions Are Surprisingly Common

Ever heard a voice inside your head or saw something that wasn’t there? You’re not alone — and it doesn’t necessarily mean there’s something wrong with you. A study of more than 30,000 people from 18 countries found that about one in 20 of us have experienced a psychotic episode at least once.


The long-term study challenges the assumption that only people with psychosis experience hallucinations and delusions, though the causes and implications of these episodes remain largely unknown. The study was led by Professor John McGrath, a psychologist from Australia’s Queensland Brain Institute. The results of his team’s work can now be found at JAMA Psychiatry.

“When I trained in psychiatry we were told that if you heard voices, you may have had schizophrenia and that the two were very tightly linked,” McGrath told ABC Science. “But it turns out that when you interview people in the community and ask them if they’ve ever heard voices, they’ll say ‘yes, I have had that experience before’. That’s a really important clue as to which part of the brain may be going wrong — that the circuits in the brain that underline language, hearing and speaking are tending to misfire.”

A psychotic episode (PE) is when an individual experiences a temporary break from reality. It typically involves seeing, hearing, and believing things that aren’t real. The National Alliance on Mental Illness offers some examples of hallucinations and delusions:

  • Voices telling you to commit acts of violence or self-harm.
  • Feeling like something is crawling under your skin.
  • Seeing someone take the shape of something [they are] not, such as a demon.
  • Believing external forces are controlling your thoughts, feelings and behavior.
  • Believing that trivial remarks, events or objects have personal meaning or significance.
  • Thinking you have special powers, are on a special mission or even that you are God.

It’s important to note that psychosis is not an illness unto itself, but a symptom; a PE can be the result of a mental or physical illness, substance use, trauma, extreme stress, or other factors.

After surveying 31,261 “mostly high-functioning” people, i.e. a random sampling of individuals from 18 different countries, the researchers found that the lifetime prevalence of ever having a PE is 5.8%, so they’re typically rare. Of those who experience a PE, about one-third (32.2%) only experience them once over the course of their life. About another third (31.8%) reported experiencing between two to five episodes during their life. The researchers also found that hallucinations are much more common than delusions (5.2% vs. 1.3% respectively).


The researchers conclude by saying:

The epidemiologic features of PEs are more nuanced than previously thought. Research is needed that focuses on similarities and differences in the predictors of the onset, course, and consequences of distinct PEs.


Indeed, this research should motivate psychologists to acquire a deeper understanding of the underlying mechanisms involved. Moreover, it should influence them to change the way they view psychosis and how they make their clinical diagnoses.

As McGrath told ABC Science: “We need to equip the community to understand that it’s OK to talk about your depression, you should seek help if you hear voices, or you should seek help if you’re suicidal because these are things that we can help you with. I think as a community we need to be more aware of that — these are everyday things that are happening to everyday people.”


More at ABC Science. And check out the entire study at JAMA Psychiatry: “Psychotic Experiences in the General Population: A Cross-National Analysis Based on 31 261 Respondents From 18 Countries”.

Email the author at george@io9.com. Top image by agsandrew/Shutterstock.




Believing that trivial remarks, events or objects have personal meaning or significance.

Well then, there are a lot of folks hallucinating out there a lot of the time.