In the last decade, there has been an increasing interest in cognitive alterations during the early course of schizophrenia. From a clinical perspective, a better understanding of cognitive functioning in putative at-risk states for schizophrenia is essential for developing optimal early intervention models. Two approaches have more recently been combined to assess the entire course of the initial schizophrenia prodrome: the predictive "basic symptom at-risk" (BS) and the ultra high-risk (UHR) criteria. Basic symptoms are considered to be present during the entire disease progression, including the initial prodrome, while the onset of symptoms captured by the UHR criteria expresses further disease progression toward frank psychosis. The present study investigated the cognitive functioning in 93 subjects who met either BS or UHR criteria and thus were assumed to be at different points on the putative trajectory to psychosis. We compared them with 43 patients with a first episode of psychosis and to 49 help-seeking patient controls. All groups performed significantly below normative values. Both at-risk groups performed at intermediate levels between the first-episode (FE) group and normative values. The UHR group demonstrated intermediate performance between the FE and BS groups. Overall, auditory working memory, verbal fluency/processing speed, and declarative verbal memory were impaired the most. Our results suggest that cognitive impairments may still be modest in the early stages of the initial schizophrenia prodrome and thus support current efforts to intervene in the early course of impending schizophrenia because early intervention may prevent or delay the onset of frank psychosis and thus prevent further cognitive damage.

Recent research has attempted to improve the identification of individuals at-risk of developing schizophrenia to permit targeted early prevention. Two sets of criteria, one characterized by a subgroup of 'basic symptoms' [Klosterkötter, Hellmich, Steinmeyer, Schultze-Lutter (2001) Arch Gen Psychiat 58:158-164] and one by the ultra high-risk model [Miller, McGlashan, Woods, Stein, Driesen, Corcoran, Hoffman, Davidson (1999) Psychiatr Q 70:273-287; Yung, McGorry, McFarlane, Jackson, Patton, Rakkar (1996) Schizophr Bull 22:283-303], have been associated with positive predictive values for later schizophrenia. This paper is a critical discussion of these predictive values. In the first part, the paper demonstrates that the predictive values of at-risk criteria are mediated by a strong enrichment effect and depend considerably on the structure of early detection systems. Further, it shows that these predictive values do not apply to the general population level, where subclinical psychosis shows high prevalence and incidence rates, and that these values may be less predictive in adolescents. In the second part, the paper discusses the need for specific sensitization on several levels of an early detection system and proposes a selected overview of prototypical models already applied in this field.

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