Hallucinations and delusions in the general population are more common than previously thought.
An international study led by The University of Queensland and Harvard Medical School found that hearing voices and seeing things others cannot impacts about five per cent of the general population at some point in their lives.
Queensland Brain Institute researcher Professor John McGrath said the study, involving more than 31,000 people from 19 countries, was the most comprehensive ever completed.
“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 McGrath said.
“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.”
The study was a population-based survey which involved approaching randomly selected members of the community, sitting down with them and conducting a very detailed interview about their mental health.
“These people were representative of the general population, not seeking mental health assistance,” Professor McGrath said.
The study found that auditory hallucinations are more common in women than men, and they are also more common in people from wealthier countries.
Professor McGrath said the findings could help generate new research into the causes of these isolated symptoms.
“In particular, we are interested in learning why some people recover, while others may progress to more serious disorders such as schizophrenia,” he said.
“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.
“While people may experience a false perception such as mistakenly hearing their name called out in public, hallucinations and delusions are quite detailed, for example hearing voices that no one else can hear or a belief that somebody else has taken over your mind.
“People should be reassured that there isn’t anything necessarily wrong with them if it happens once or twice, but if people are having regular experiences, we recommend that they seek help.”
About this psychology research
Funding: This work was funded by a National Health and Medical Research Council John Cade Fellowship.
Source: Darius Koreis – University of Queensland Image Source: Image is in the public domain Original Research: Full open access research for “Psychotic Experiences in the General Population: A Cross-National Analysis Based on 31 261 Respondents From 18 Countries” by Sandra Siegert, Jinsoo Seo, Ester J Kwon, Andrii Rudenko, Sukhee Cho, Wenyuan Wang, Zachary Flood, Anthony J Martorell, Maria Ericsson, Alison E Mungenast and Li-Huei Tsai in JAMA Psychiatry. Published online May 27 2015 doi:10.1001/jamapsychiatry.2015.0575
Psychotic Experiences in the General Population: A Cross-National Analysis Based on 31 261 Respondents From 18 Countries
Importance: Community-based surveys find that many otherwise healthy individuals report histories of hallucinations and delusions. To date, most studies have focused on the overall lifetime prevalence of any of these psychotic experiences (PEs), which might mask important features related to the types and frequencies of PEs.
Objective: To explore detailed epidemiologic information about PEs in a large multinational sample.
Design, Setting, and Participants: We obtained data from the World Health Organization World Mental Health Surveys, a coordinated set of community epidemiologic surveys of the prevalence and correlates of mental disorders in representative household samples from 18 countries throughout the world, from 2001 through 2009. Respondents included 31 261 adults (18 years and older) who were asked about lifetime and 12-month prevalence and frequency of 6 types of PEs (2 hallucinatory experiences and 4 delusional experiences). We analyzed the data from March 2014 through January 2015.
Main Outcomes and Measures: Prevalence, frequency, and correlates of PEs.
Results: Mean lifetime prevalence (SE) of ever having a PE was 5.8% (0.2%), with hallucinatory experiences (5.2% [0.2%]) much more common than delusional experiences (1.3% [0.1%]). More than two-thirds (72.0%) of respondents with lifetime PEs reported experiencing only 1 type. Psychotic experiences were typically infrequent, with 32.2% of respondents with lifetime PEs reporting only 1 occurrence and 31.8% reporting only 2 to 5 occurrences. We found a significant relationship between having more than 1 type of PE and having more frequent PE episodes (Cochran-Armitage z = −10.0; P < .001). Lifetime prevalence estimates (SEs) were significantly higher among respondents in middle- and high-income countries than among those in low-income countries (7.2% [0.4%], 6.8% [0.3%], and 3.2% [0.3%], respectively; χ22 range, 7.1-58.2; P < .001 for each) and among women than among men (6.6% [0.2%] vs 5.0% [0.3%]; χ21 = 16.0; P < .001). We found significant associations with lifetime prevalence of PEs in the multivariate model among nonmarried compared with married respondents (χ22 = 23.2; P < .001) and among respondents who were not employed (χ24 = 10.6; P < .001) and who had low family incomes (χ23 = 16.9; P < .001).
Conclusions and Relevance: 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.
“The schizophrenia risk gene product miR-137 alters presynaptic plasticity” by Sandra Siegert, Jinsoo Seo, Ester J Kwon, Andrii Rudenko, Sukhee Cho, Wenyuan Wang, Zachary Flood, Anthony J Martorell, Maria Ericsson, Alison E Mungenast & Li-Huei Tsai in Nature Neuroscience. Published online May 25 2015 doi:10.1038/nn.4023