Early stages of schizophrenia

Vol 7 n° 1 - Early stages of schizophrenia

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he detection of psychotic disorder in the prodromal

phases, coupled with specialized early interventions to pre-

vent transition to overt psychotic disorder, has become the

subject of an increasing amount of research and debate.^1-8

Although this issue is by no means new,^9,10 it is only in the last

few years that the outlines of a consensus, based on quanti-

tative arguments,are becoming discernible.These will be dis-

cussed in this article, using data from several population-

based investigations to illustrate the quantitative arguments.

Jim Van Os, MD, PhD; Philippe Delespaul, MA, PhD

Keywords: prediction; screening; schizophrenia; psychotic disorder; specificity;

Author affiliations: Department of Psychiatry and Neuropsychology, South

Limburg Mental Health Research and Teaching Network, European Graduate

School of Neuroscience, Maastricht University, The Netherlands (Jim Van Os,

Philippe Delespaul); Division of Psychological Medicine, Institute of

Address for correspondence: Prof Jim Van Os, Department of Psychiatry and

Neuropsychology, PO Box 616 (DRT10), 6200 MD Maastricht, The Netherlands

Screening for preschizophrenia in the general population with the aim of preventing transition to full-blown illness

is an epidemiological impossibility because a rare disease cannot be predicted. The lack of specificity resulting in abun-

dance of false-positives can be remedied in part by using much more restrictive screening criteria that combine sev-

eral indicators of risk for transition to schizophrenia. Raising the specificity (reducing the false-positives), however, can

only be done at the expense of sensitivity (increasing the false-negatives). The most commonly used strategy to raise

specificity is the sample enrichment strategy. This involves the creation of samples enriched with schizophrenia risk by

selectively filtering at-risk people out over a range of consecutive referral processes starting in the general popula-

tion, through to general practioners, mental health services, and the early detection clinic. However, improvements

in specificity obtained by the sample enrichment strategy should not be attributed to the use of some predictive instru-

ment that supposedly identifies high-risk individuals. The epidemiologically and ethically most viable way for screen-

ing and early detection is to selectively increase the permeability of the filters on the pathway to mental health care.

This will occasion samples of help-seekers enriched with schizophrenia risk at the level of mental health services (thus

reducing false-positives), while at the same time making an attempt to “attract” as many detectable schizophrenia

prodromes as possible through the filters along the pathway to mental health care (thus reducing false-negatives).

Early psychosis research has yielded some useful suggestions in that it is becoming increasingly clear that it is not

just psychosis itself, but rather the clinical context of the psychotic experience that determines risk for transition to

schizophrenia. Thus, risk for transition to full-blown psychotic disorder is to a large degree determined by size of psy-

chosis “load,” comorbid distress and depression, cannabis use, cognitive ability, and subjective reports of impairment

and coping. Making a diagnosis of psychotic disorder is not an exact science: it involves an arbitrary cutoff imposed

on dimensional variation of psychopathology and need for care over time. Gaining insight into the cognitive and bio-

logical factors that drive the dimensional variation, including therapeutic interventions, is arguably more useful than