To test if specific correlations exist between cognitive measures and psychotic dimensions in schizophrenic subjects and if similar correlations, between cognition and schizotypal dimensions, are present in non-psychotic subjects.

We administered the same battery of cognitive tests (Source Monitoring, Verbal Fluency [VF] and Stroop tests) to schizophrenic subjects (N = 54), their first-degree relatives (N = 37) and controls (N = 41). Scores of negative, positive and disorganisation dimensions were derived from the Signs and Symptoms of Psychotic Illness scale in schizophrenic subjects, and from the Schizotypal Personality Questionnaire in relatives and controls.

In schizophrenic subjects, as hypothesised, the negative dimension correlated with performance on VF and disorganisation with performance in the Stroop test. The positive dimension did not correlate with any cognitive measure.

With only one exception, the significant correlations observed in non-psychotic subjects did not match correlations seen in schizophrenic subjects. In non-psychotic subjects greater disorganisation was associated with more clustered words in VF suggesting that excessive automatic spreading of activation in semantic networks could underlie this dimension.

As a whole, data lent partial support to our hypothesis of specific cognitive–clinical correlations in schizophrenic subjects but did not support the existence of similar correlations in non-psychotic subjects.

Executive dysfunctions have been studied as a potential endophenotype associated with the genetic basis of autism. Given that recent findings from clinical and molecular genetic studies suggest that autism and obsessive-compulsive disorder (OCD) could share a common pattern of heritability, we assessed executive functions as a possible common cognitive endophenotype in unaffected family members of individuals with either autism or OCD.

Five tests assessing executive functions (Tower of London, verbal fluency, design fluency, trail making and association fluency) were proposed to 58 unaffected first-degree relatives (parents and siblings) of probands with autism and 64 unaffected first-degree relatives of OCD patients. Results were compared with those of 47 healthy controls matched for age, sex, and level of education.

In the Tower of London test, both groups of unaffected relatives showed significantly lower scores and longer response times compared with controls. No differences were observed between autism and OCD relatives and healthy controls in the four other tasks (verbal fluency, design fluency, trail making test and association fluency).

Our findings show the existence of executive dysfunction in the unaffected first-degree relatives of probands with OCD, similar to those observed in the relatives of patients with autism. These results support and extend previous cognitive studies on probands indicating executive dysfunctions in autism and OCD. Planning and working memory processes could thus represent a common cognitive endophenotype in autism and OCD that could help in the identification of genes conferring vulnerability to these disorders.

Schizoaffective disorder could be considered as a form of schizophrenia, a form of bipolar disorder, an independent disorder or a disorder intermediate between bipolar disorder and schizophrenia, within a psychotic continuum. The study of cognitive deficits in subjects with those diagnoses could help differentiate between these possibilities.

We compared cognitive performances of schizoaffective (SZAff) subjects with those of subjects with schizophrenia (SZ), bipolar disorder with psychotic symptoms (life-time) (BDP), bipolar disorder without life-time occurrence of psychotic symptoms (BD) and normal controls (NC). We used two tests of executive functions – the Wisconsin Card Sorting Test (WCST) and the Trail-making Test (TMT) – that are known to be impaired in those disorders.

The number of perseverative errors on WCST was highest in SZ subjects and gradually decreased in SZAff, BDP and, finally in BD subjects. By contrast, SZ and SZAff subjects obtained similar scores in the TMT, as did BD and BDP patients.

These results suggest that, for some deficits, there may be a continuum between SZ, SZAff and affective disorders, whereas SZAff patients most closely resemble SZ patients for other deficits. This implies that different conceptual views about schizoaffective disorder should be seen as complementary, rather than mutually exclusive.

A wide range of cognitive deficits have been demonstrated in schizophrenia, but their longitudinal course remains unclear.

To bring together all the available information from longitudinal studies of cognitive performance in people with schizophrenia.

We carried out a meta-analysis of 53 studies. Unlike previous reviewers, we included all studies (regardless of the type of medication), analysed each variable separately and compared results with data from controls.

Participants with schizophrenia showed a significant improvement in most cognitive tasks. The available data for controls showed, with one exception (the Stroop test), a similar or greater improvement. Performance in semantic verbal fluency remained stable in both individuals with schizophrenia and controls.

Participants with schizophrenia displayed improvement in most cognitive tasks, but practice was more likely than cognitive remediation to account for most of the improvements observed. Semantic verbal fluency may be the best candidate cognitive endophenotype.