It turns out hallucinations and delusional thoughts are more common among people than previously assumed, according to a new international study out of the University of Queensland and Harvard Medical School.

The study found that hearing voices, seeing things, and other symptoms that are typically associated with psychosis or schizophrenia actually occur in about 5 percent of the general population at some point in their life. As a result, the authors posit that hallucinations don’t always have to be associated with mental illness.

“We used to think that only people with psychosis heard voices or had delusions, but now we know that otherwise healthy, high-functioning people also report these experiences,” Professor John McGrath, an author of the study, said in the press release. “Of those who have these experiences, a third only have them once and another third only have two-to-five episodes across their life. These people seem to function reasonably well. So it’s incredibly interesting that not only is hearing voices more common than previously thought, but it’s not always linked to serious mental illness.”

In the study, researchers examined 31,000 people from 19 different countries, questioning them about their overall mental health. They found that sound hallucinations were more likely to occur in women than in men, as well as people who were from richer countries. Ultimately, they hope this information will help them learn more about the causes of severe hallucinatory disorders — as well as ways to mitigate the effects.

“In particular, we are interested in learning why some people recover, while others may progress to more serious disorders such as schizophrenia,” McGrath said in the press release. “We need to understand why it’s temporary for some people and permanent for others. We can use these findings to start identifying whether the mechanisms causing these hallucinations are the same or different in both situations. We need to rethink the link between hearing voices and mental health — it’s more subtle than previously thought.”

Source: McGrath J et al. Psychotic Experiences in the General Population: A Cross-National Analysis Based on 31 261 Respondents From 18 Countries. JAMA Psychiatry, 2015.