Psychotic symptoms in non-clinical populations and the continuum of psychosis

doi:10.1016/S0920-9964(01)00352-8

Schizophrenia Research

Volume 54, Issues 1–2, 1 March 2002, Pages 59-65

https://doi.org/10.1016/S0920-9964(01)00352-8 Get rights and content

Abstract

A growing body of evidence suggests that delusional or hallucinatory experiences are much more frequent in subjects from the general population than the prevalence of cases of psychotic disorders, thereby suggesting the existence of a symptomatic continuum between subjects from the general population and clinical cases of psychosis. Exploring the risk factors modulating the expression of psychosis-like signs in non-clinical populations may better contribute to elucidate the etiology of psychosis than research restricted to subjects at the endpoint of the distribution of the psychotic dimension. The aim of this paper is to briefly review research investigating the distribution of psychotic symptoms in non-clinical populations, the developmental aspects of psychosis proneness, and the outcome characteristics of psychosis-prone subjects.

Introduction

Dichotomization of psychotic symptoms as either absent or present is a convenient concept for diagnostic process and medical decision-making (Rose, 1992). Medical research on psychosis has been strongly influenced by this categorical approach, and has been mainly focused on subjects identified as “case of psychosis” according to these medical criteria, i.e., as “case in need of treatment” van Os et al., 1999a, van Os and Verdoux, in press.

A challenging approach initiated several decades ago postulates that light may be shed on the etiology of psychosis by studying subjects presenting psychosis-like experiences (or “schizotypal” signs) without reaching the clinical threshold of being defined as “case in need of treatment” Meehl, 1962, Venables, 1995, Venables et al., 1990. Two complementary strategies have been used to explore schizotypal phenomena in non-clinical populations Claridge, 1997, Claridge and Beech, 1995, Venables and Rector, 2000. A first approach is based upon a “fully” dimensional model taking “normality” as the reference point Claridge, 1997, Claridge and Beech, 1995, and conceptualizing schizotypy/psychosis proneness as a dimensional trait ranging from “normality” to clinical cases of psychosis. A slightly different approach is based upon a “quasi”-dimensional model taking the abnormal state as the reference point Claridge, 1997, Claridge and Beech, 1995, and focused on the exploration of attenuated or full-blown psychotic symptoms in non-clinical populations.

The aim of this paper is to briefly review research based upon the quasi-dimensional model of psychosis investigating the distribution and the characteristics associated with psychotic symptoms in non-clinical populations.

Section snippets

Distribution of psychotic symptoms in non-clinical populations

According to the continuum hypothesis, psychotic symptoms should be present not only in subjects identified as “cases of psychosis”, but also in a proportion of subjects from the general population that does not fulfill the clinical criteria of “case of psychosis”. Studies carried out in non-clinical populations using structured diagnostic interviews have demonstrated that psychotic experiences and beliefs are quite common in these samples van Os and Verdoux, in press, van Os et al., 1999a. For

Characteristics associated with psychosis proneness in non-clinical populations

If a symptomatic continuum exists between subjects from the general population and clinical cases of psychosis, this continuum should also be apparent for the developmental aspects of delusional formation. In clinical cases of psychosis, age has a strong influence on the symptomatic expression of the disease. In functional psychoses, the likelihood to present with delusion increases with age at onset from puberty to early adulthood (Galdos and van Os, 1995). During adulthood, delusional

Psychiatric outcome of subjects with psychosis proneness

Although psychosis proneness is considered as a risk factor for schizophrenia, few studies have explored the psychiatric outcome of psychosis-prone subjects. Chapman et al. (1994) reported that high baseline scores on the perceptual aberration and/or the magical ideation (Per-Mag) scales predicted not only a higher frequency of psychosis or psychosis-like experiences over the next 10 years, but also a higher rate of mood disorders. Among the 182 subjects with high Per-Mag scores, 10 (0.5%)

Conclusion

Although the clinically driven categorical model of psychosis has strongly influenced psychiatric research on psychotic phenomena, a growing body of evidence has now confirmed the heuristic interest of the alternative concept which takes psychosis as a dimensional phenomenon lying on a continuum with normality. Exploring the distribution of psychosis-like signs in non-clinical populations and the risk factors modulating their expression may better contribute to elucidate the risk factors for

Acknowledgements

We acknowledge Ray Cooke who kindly supervised the English of this paper. We are most grateful to the general practitioners of the Aquitaine Sentinel Network, and to all the primary care patients who collaborated in the Aquitaine survey on delusional ideation. We thank Sylvie Maurice-Tison and Bernard Gay who assisted in the organization of the survey.

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Psychotic symptoms in non-clinical populations and the continuum of psychosis

Abstract

Introduction

Section snippets

Distribution of psychotic symptoms in non-clinical populations

Characteristics associated with psychosis proneness in non-clinical populations

Psychiatric outcome of subjects with psychosis proneness

Conclusion

Acknowledgements

Schizophr. Res.

Schizophr. Res.

J. Psychiatr. Res.

Schizophr. Res.

Schizophr. Res.

Pers. Individ. Differ.

Schizophr. Res.

Compr. Psychiatry

Putatively psychosis-prone subjects 10 years later

J. Abnorm. Psychol.

Theorical background and issues

Fully and quasi-dimensional constructions of schizotypy

The factor structure of “schizotypal” traits: a large replication study

Br. J. Clin. Psychol.

Screening for psychosis in the general population with a self-report interview

J. Nerv. Ment. Dis.

Religious affiliation in twins and their parents: testing a model of cultural inheritance

Behav. Genet.

Is schizophrenia a disorder of all ages? A comparison of first episodes and early course across the life-cycle

Psychol. Med.

Schizophrenia: recent epidemiologic issues

Epidemiol. Rev.

Lifetime prevalence, demographic risk factors, and diagnostic validity of nonaffective psychosis as assessed in a US community sample. The National Comorbidity Survey

Arch. Gen. Psychiatry