Schizophrenia Research Trends

56Guy SandnerSubsets of the DiseaseBecause of the diversity of its symptoms and the minimal criteria used to diagnoseschizophrenia, one may wonder whether they constitute specific subsets of the disease.Statistical studies on populations of patients (cluster analyses) have identified four subsets atthe onset of the disease [112]. One third of the patients show predominant negativesymptoms. One tenth of them show predominant positive symptoms. One fifth of them showmainly signs of disorganization added to significant indexes of positive and negativesymptoms. The remaining third have been qualified as “mixed” by some authors and werefound to have all symptoms but at a low level. Whether these patients belong to a form of“mild schizophrenia” or have been tested during an interval between two active episodes isunclear. This is perhaps the reason why other authors accept only three subsets.COGNITIVE DISABILITIES IN SCHIZOPHRENIACognitive deficits have become accepted as robust and core characteristics of thedisorder to such a degree that it has been recently suggested that the diagnostic criteria forschizophrenia should be reconsidered by including a new category of “schizotaxia” in thenext edition of the DSM [86,120]. According to the present stage of the possibilities tocharacterize such deficits, it remains premature to do so in the close future. A delay isnecessary to further develop their theoretical background. Important also, will be the clearidentification of the cognitive skills that remain preserved by the disease. Another point thatrequires more research is the determination of the time course of each cognitive deficit alongthe disease. Cognitive deficits manifest before the occurrence of the first active phase andthere appears to emerge now a consensus that some of them are constant along the evolutionof the disease. The cognitive impairment observed in the adult has even been proposed to bea fossilized way of childish thinking, a failure of normal cognitive maturation. The cognitiveaspects of schizophrenia have been considered to represent a kind of “endophenotype”, moreproximal to this disease’s cause than to the symptoms. Their early manifestation has beenused as an argument in favor of the idea that schizophrenia is a neurodevelopmental disease.Being present also in relatives of patients or in schizotypal personality people they have beencalled “traits” of the disease, and suspected to account for a state of vulnerability leading tothe disease or not, depending on deleterious or protective environmental influences.Diverse cognitive functions have been found altered in patients. They will be consideredin turns, below. What they have in common is that they require an effortful psychologicalactivity, a controlled management of attention or an appropriate management of complexmemories.1. Mixed disabilities are commonly observed using the standard Wechsler AdultIntelligence Scale (WAIS IQ). Altered executive functions gather a difficulty tomanage the temporary storage of memories (working memory), a reduced access toinferential reasoning, and a decreased mental shifting capacity. Awareness, sustainedattention and vigilance may be also affected. Classical global evaluations have found