Diagnosis and Classification of the Schizophrenia Spectrum Disorders

1 The Schizophrenia Construct After 100 Years of Challenges 5(prodromal) stage of SZ, but rather as an independent diagnostic category characterizedby a slow progressive course, subclinical manifestations in the latent period,overt psychopathological symptoms in the active period, and then by a gradualreduction of positive symptoms, with negative symptoms predominating the clinicalpicture during patient stabilization [40]. Unfortunately, the “sluggish” (“latent”)form of schizophrenia has been used for political purposes in the Soviet Union.Clearly, the use of diagnoses such as sluggish schizophrenia exposes fundamentaldeficiencies in the reliable and valid definition and classification of psychiatricdisorders.The American model requires the presence of psychotic features, establishedchronicity, evidence of deterioration, and the exclusion of affective and organic features[41]. The diagnostic criteria for SZ in the Diagnostic and Statistical Manual ofMental Disorders (DSM-IV) [42] are based on the premise that it is a discrete illnessentity, in particular, distinct from the affective psychoses. A variety of psychoticsyndromes has been described which have features in common with the so-calledschizophrenic psychoses (DSM-IV): schizophrenia (295.x), schizophreniform disorder(295.4), schizoaffective disorder (295.7), delusional disorder (297.1), briefpsychotic disorder (298.8), shared psychotic disorder (297.3), psychotic disorderdue to (specify medical condition, 293.x), substance-induced psychotic disorders(293.x), delusional disorder (297.1), psychotic disorder NOS (298.9). The validityof schizophreniform disorder (295.4), brief psychotic disorder (298.8), and sharedpsychotic disorder (297.3) remains controversial and their diagnosis has limitedclinical utility. For instance, findings from prior research suggests that cases ofschizophreniform disorder may be: (1) atypical cases of affective disorders, (2) casesof schizophrenia in early course, or (3) a heterogeneous group of disorders includinga subgroup with benign course and outcome that maintains this diagnosis forless than 6 months.The International Classification of Diseases and related Health Problems (TenthRevision; ICD-10) [43] classifies SZ together with schizotypal disorder, persistentdelusional disorder, acute and transient psychotic disorders, induced delusionaldisorder and schizoaffective disorder. This classification avoids criteria based onsocial and occupational dysfunction for the diagnosis of SZ on the grounds that it isdifficult to compare these criteria across different cultures.Thus, in the current categorical classifications of diseases (DSM-IV and ICD-10),SZ, as well as other disorders, are seen as a categorical entity that includes bothclinical (symptoms) and outcome (duration) items. However, because the definitionof SZ requires only a certain number of items without any preference, it isnot uncommon for two patients with the same diagnosis to have almost totally differentsymptomatology, while outcomes within the SZ diagnosis vary considerably[29]. The diagnostic criteria for SZ are based on the premise that it is a discreteillness entity, in particular, distinct from the affective psychoses. This assumptionhas persisted for more than a century, even though patients with a diagnosis ofschizophrenia show a wide diversity of symptoms and outcomes, and no biologicalor psychological feature has been found to be pathognomonic of the disorder[26, 44–46].