A new international study has found that hallucinations and delusions can occur among people without a mental illness, although the odds are small.

Researchers from the University of Queensland, Australia, discovered hearing voices and seeing things others cannot impacts about five percent of the general population at some point in their lives.

John J. McGrath, Ph.D., M.D. conducted the study as interest in the prevalence of hallucinations and delusions has grown because these psychotic experiences (PEs) are reported by a sizable minority of the population.

McGrath and coauthors examined data collected in the World Health Organization World Mental Health surveys. The data came from 18 countries across North and South America, Africa, the Middle East, Asia, the South Pacific, and Europe.

Respondents included 31,261 adults who were asked about the prevalence and frequency of PEs. As reported online in JAMA Psychiatry, the study found the lifetime prevalence of at least one PE was reported by 5.8 percent of the 31,261 survey respondents.

The lifetime prevalence of any hallucinatory experience (HE) was 5.2 percent and of any delusional experience (DE) was 1.3 percent.

Lifetime prevalence estimates of PEs were higher among women (6.6 percent) than men (five percent) and higher among those individuals who lived in middle-income (7.2 percent) and high-income (6.8 percent) countries than in low-income countries (3.2 percent), according to the results.

These psychotic experiences were infrequent with 32.2 percent of respondents with lifetime PEs reporting only one episode and an additional 31.8 percent of respondents with lifetime PEs having experienced two to five episodes.

“We have provided, to our knowledge, the most comprehensive description of the epidemiologic landscape of PEs published to date. Although the lifetime prevalence of PEs is 5.8 percent, these events are typically rare,” according to the authors.

“The research community needs to leverage this fine-grained information to better determine how PEs reflect risk status. Our study highlights the subtle and variegated nature of the epidemiologic features of PEs and provides a solid foundation on which to explore the bidirectional relationship between PEs and mental health disorders,” the study concludes.

Source: JAMA Psychiatry/EurekAlert!