Empirically based qualitative and quantitative variations on the psychosis continuum in the ‘HowNutsAreTheDutch’ population sample

Background: Subclinical psychotic experiences are common in the general population and form a paradox. On the one hand, psychotic experiences have a relatively high prevalence in the general population and the majority of such experiences is transient. Even most individuals considered to be at Ultra High Risk (UHR) do not develop a clinical psychotic disorder. On the other hand, psychotic experiences are associated with a large number of concurrent mental health problems. Even in individuals at UHR who do not develop a clinical psychotic disorder, psychotic experiences are associated with mental health problems and poorer psychosocial functioning. A challenge for both researchers and clinicians is to adequately distinguish those with benign experiences from those with more pathological psychotic experiences. One possible explanation for this is that most research on psychotic experiences has focused exclusively on positive psychotic experiences. However, psychosis is currently conceptualized as a multidimensional construct. Another possible explanation may be that they form a heterogeneous concept as not all
experiences may be pathological in nature. The goal of the present study was to perform quantitative and qualitative examinations of the heterogeneity of individuals reporting subclinical psychotic experiences in a unique Dutch internet-based general population sample.

Methods: The HowNutsAreTheDutch study is a large-scale crowdsourcing project, and its aims are twofold: to (i) investigate the continuity of multiple mental health dimensions in the Dutch population and (ii) gain more insight into the interactions between mental strengths and mental vulnerabilities/problems. Positive and negative subclinical psychotic experiences were measured with the Community Assessment of Psychic Experiences (CAPE) in n = 2870 individuals. The prevalence of these experiences and their associations with demographics, affect, psychopathology and quality of life were investigated first. Next, Latent Class Analysis (LCA) was used to identify data-driven subgroups with different symptom patterns. These subgroups were also compared on aforementioned factors.

Results: Subclinical psychotic experiences were commonly reported. Prevalence rates differed strongly between items, ranging from 1-89% (mean: 21% for positive and 56% for negative experiences). Both positive and negative psychotic experiences were associated with younger age, more negative affect, anxiety and depression and less positive affect and quality of life. Seven latent classes were identified that were labeled as ‘Mentally fit’, ‘Lethargic’, ‘Blunted’, ‘Distressed’, ‘Spiritual’, ‘Grandiose’, and ‘Pathological’. These classes demonstrated both quantitative differences in the number/severity of reported psychotic experiences and qualitative differences in the patterns of reported experiences.

Discussion: Subclinical psychotic experiences show both dimensional severity variations and discrete symptom pattern variations across individuals in the general population, suggesting that, to understand and capture all interindividual variations in subclinical psychotic experiences, their number, nature and context should all be considered at the same time. Only some psychotic experiences may lay on a true psychopathological psychosis continuum. Taking into account the base rate in the population as well as the context of psychotic experiences (i.e. the larger pattern in which they occur) could help to determine whether such experiences should be interpreted as a warning signal or not. This may help us to identify those individuals who are at most risk for developing mental health problems and may guide services of early detection and intervention