Pathways to schizophrenic psychosis: A LISREL-tested model of the unfolding of the schizophrenic prodrome

Abstract

In this article a literature-based model (the Schizotypic Syndrome Questionnaire [SSQ] model) is presented that gives a description of the temporal unfolding of the schizophrenic prodrome. As a guiding principle for the selection of the symptoms in the model, the hypothesis was held that the main prodromal features determine each other in terms of cause and effect. Furthermore, the developmental pathways between the symptoms were not allowed to be in conflict with the usual observation that negative symptoms precede psychotic-like ones nor--at least in broad outline--with J.P. Docherty, D.P. van Kammen, S.G. Siris, and S.R. Marder's (1978) description of the various onset stages in the development of a schizophrenic psychosis. For the definitive version of the SSQ model, 12 symptoms were selected (e.g., affective flattening, suspicion, and delusional thinking). After specifying the paths to be estimated, the model was examined in two randomly drawn samples from a total community-based sample of 771 normal subjects and in the total sample itself, in each case resulting in adequate fit values. Moreover, all postulated pathways were found to be significantly different from zero. The use of a normal sample was based on the continuum hypothesis. Given the present-day discussions concerning the tenability of the schizophrenia concept, the model's implications with respect to that issue are particularly emphasized. Furthermore, the concept of the schizophrenia prodrome itself is critically discussed.

Personality and Psychopathology: a Theory-Based Revision of Eysenck’s PEN Model

“…Moreover, the validity of the EPQ P scale seems indicated by the fact that the scale, as regards content, agrees well with former descriptions of the schizoid personality, which may not only be present among biological relatives of schizophrenics, but may also be observed prior to schizophrenic breakdown [73]. It is this psychopathic content that makes the EPQ P scale a measure of those personality characteristics that are elsewhere described as defining the schizotypy factor Impulsive Nonconformity [74] or Asocial Schizotypy [53,75], and not a measure of those features associated with the remaining schizotypy factors Positive Schizotypy, Negative Schizotypy, and Cognitive Disorganization. Given this limitation, it seems not only appropriate to replace the usual idea of one single, unobservable, and continuously distributed variable termed liability or predisposition to schizophrenia [76] by a model in which three [75] or four [74] vulnerability factors operate, but also to redefine Eysenck’s EPQ P dimension as a factor that only accounts for the emergence of antisocial conduct, both in prodromal and full-blown schizophrenia, and also in schizoid disease [75].…”

“…On this continuum, Absorption is assumed to lead to depersonalization and derealization (dissociative detachment), and may finally result in an inward flight into a world of traumatic images and affects, ‘with all the earmarks of psychotic experience’. Recent research by Van Kampen, Maurer, An der Heiden & Häfner [106], testing Van Kampen’s [53] SSQ model of prodromal unfolding in a sample of first-episode schizophrenic patients, corroborates this view in that it could demonstrate that four symptoms indicative of a process of progressive estrangement on Allen & Coyne’s detachment continuum had their mean times of onset associated with gradually higher positions on a standardized continuum that reflects proportion of total prodrome time.…”

“…Of course, there are recent linkage studies that suggest that schizophrenia and manic-depression share some susceptibility genes [50], but if these syndromes are defined as usual on the basis of a lifetime diagnostic hierarchy with schizophrenia at the top and bipolar disorder at a lower position, quantitative genetic studies have generally not demonstrated significant familial co-aggregation [51]. Moreover, a relaxation of that hierarchy – permitting, for instance, the recognition of mania as a separate disorder in the presence of typical schizophrenia – must be criticized, for it is known that the decompensation process in schizophrenia includes the occurrence of manic- and depressive-like symptoms [52,53]. With respect to other forms of psychosis (for instance, delusional and schizo-affective disorder), a genetic relationship with schizophrenia cannot be excluded [54], but these relationships hardly carry any weight here, as at least some of these conditions may simply be subsumed under the category of schizophrenic disorders, because the boundaries of the schizophrenia concept are still unclear [55].…”

Processes of Inference, Schizotypal Thinking, and Obsessive-Compulsive Behaviour in a Normal Sample

“…The questionnaire was specifically developed to detect schizotypal symptoms in a normal sample (van Kampen, 2005). Items are scored on a 4-point scale 3: YES, 2: yes, 1: no, 0: NO.…”

The 5-Dimensional Personality Test (5DPT): Relationships With Two Lexically Based Instruments and the Validation of the Absorption Scale

“…As the dimensions E and N in Eysenck's PEN model are also vulnerability factors for schizophrenia and affective disorders (see Van Kampen, 1993, the finally restored PEN model is composed of five distinct personality factors-Absorption (A), Orderliness (G), Extraversion (E), Neuroticism (N), and Insensitivity (S)-thereby constituting the acronym AGENS. These factors, although basically normal, are believed to create a personality taxonomy of clinical relevance, addressing both the core symptoms of disordered personality that appear to be continuous with normal personality (e.g., Coolidge, Segal, Cahill, & Archuleta, 2008) and the causal relationships between normal personality and Axis I clinical syndromes (see, for schizophrenia, Van Kampen, 2005, 2006b.…”