A preliminary report of a strong genetic component for thought disorder in normals. A twin study

Linkage and whole genome sequencing identify a locus on 6q25-26 for formal thought disorder and implicate MEF2A regulation

Formal thought disorder is a major feature of schizophrenia and other psychotic disorders. It is heritable, found in healthy relatives of patients with schizophrenia and other mental disorders but knowledge of specific genetic factors is lacking. The aim of this study was to search for biologically relevant high-risk variants. Formal thought disorder was assessed in participants in the Copenhagen Schizophrenia Linkage Study (N=236), a unique high-risk family study comprised of six large pedigrees. Microsatellite linkage analysis of formal thought disorder was performed and subsequent haplotype analysis of the implicated region using phased microsatellite and SNP genotypes. Whole genome sequencing (N=3) was used in the attempt to identify causative variants in the linkage region. Linkage analysis of formal thought disorder resulted in a single peak at chromosome 6(q26-q27) centred on marker D6S1277, with a maximum LOD score of 4.0. Phasing and fine mapping of the linkage peak identified a 5.5Mb haplotype (chr6:162242322-167753547, hg18) in 31 individuals, all belonging to the same pedigree sharing the haplotype from a common ancestor. The haplotype segregated with increased total thought disorder index score (P=4.9 × 10(-5)) and qualitatively severe forms of thought disturbances. Whole genome sequencing identified a novel nucleotide deletion (chr6:164377205 AG>A, hg18) predicted to disrupt the potential binding of the transcription factor MEF2A. The MEF2A binding site is located between two genes previously reported to associate with schizophrenia, QKI (HGNC:21100) and PDE10A (HGNC:8772). The findings are consistent with MEF2A deregulation conferring risk of formal thought disorder.

Thought disorder in mid-childhood as a predictor of adulthood diagnostic outcome: findings from the New York High-Risk Project

BACKGROUND

Thought disorder has been proposed as an indicator of schizotypy, which is considered to be necessary but not sufficient for the development of schizophrenia. It is unclear whether thought disorder is an indicator of susceptibility (i.e. an endophenotype) for schizophrenia. The goal of the present study was to elucidate the role of thought disorder in relation to schizotypy by examining its presence in high-risk individuals during mid-childhood. Method The sample consisted of 265 subjects drawn from the New York High-Risk Project. Individuals at high risk for schizophrenia (i.e. offspring of parents with schizophrenia) were compared with individuals at low risk for schizophrenia (i.e. offspring of parents with affective disorder or offspring of psychiatrically normal parents). Videotaped interviews were rated for thought disorder using the Scale for the Assessment of Thought, Language, and Communication (TLC). The same subjects were administered diagnostic interviews in late adolescence/early adulthood.

RESULTS

Although positive thought disorder was equally present in subjects with affective and non-affective psychoses, negative thought disorder (namely, poverty of speech and poverty of content of speech) was elevated only in subjects with schizophrenia-related psychosis. Logistic regression analyses revealed that negative thought disorder added to the prediction of schizophrenia-related psychosis outcomes over and above positive thought disorder.

CONCLUSIONS

These findings suggest that negative thought disorder may have a specific association with schizotypy, rather than a more general association with psychosis. The findings also support consideration of negative thought disorder as an endophenotypic indicator of a schizophrenia diathesis.

Thought disorder in offspring of schizophrenic parents: findings from the New York High-Risk Project

The goal of the present analyses was to examine the hypothesis that mild forms of thought disorder (TD) may serve as an indicator of genetic liability for schizophrenia. A subset of 232 subjects drawn from the New York High-Risk Project was used to compare individuals at high risk for schizophrenia (ie, offspring of parents with schizophrenia; n = 63) with 2 groups of individuals at low risk for schizophrenia (ie, offspring of parents with affective disorder [n = 52] and offspring of psychiatrically normal parents [n = 117]). Subjects were administered the Rorschach Inkblot Test, and their responses were assessed according to the Thought Disorder Index (TDI). The high-risk offspring displayed significantly more TD than the other 2 groups, as shown by significantly higher TDI scores. Moreover, they had more deviant verbalizations, according to their significantly higher scores on a composite Idiosyncratic Verbalizations score. As expected, the offspring who developed psychosis produced more TD in adolescence than those who did not develop psychosis. In the sample as a whole, TD scores during late adolescence/early adulthood were positively associated with schizotypal features during mid-adulthood. These findings support the assertion that the presence of TD serves as an endophenotypic marker of a schizophrenia diathesis.

Illogical thinking and thought disorder in maltreated children

OBJECTIVE

To examine illogical thinking in children from low-income families with and without histories of child maltreatment.

METHOD

Maltreated (n = 91) and nonmaltreated (n = 43) school-age children individually participated in a story game designed to elicit speech samples. Children were instructed to listen to two recorded stories and prompted to retell the story; they then were asked to create their own story from possible topics. Child behavior ratings on the Child Behavior Checklist were completed by research assistants following 35 hours of observation.

RESULTS

Maltreated children exhibited more illogical thinking than did nonmaltreated children, and the level of illogical thinking in maltreated children was in the clinically pathological range. The occurrence of multiple subtypes of maltreatment and the chronicity of the maltreatment also were associated with illogical thinking. Dissociation did not differ between groups, although it was related to illogical thinking.

CONCLUSION

The ability to formulate ideas and communicate them logically is compromised in children who have been maltreated. These results extend prior research on selective attentional processes and negativity biases in maltreated children.

The Genetic Basis of Thought Disorder and Language and Communication Disturbances in Schizophrenia

Thought disorder as well as language and communication disturbances are associated with schizophrenia and are over-represented in clinically unaffected relatives of schizophrenics. All three kinds of dysfunction involve some element of deviant verbalizations, most notably, semantic anomalies. Of particular importance, thought disorder characterized primarily by deviant verbalizations has a higher recurrence in relatives of schizophrenic patients than schizophrenia itself. These findings suggest that deviant verbalizations may be more penetrant expressions of schizophrenia susceptibility genes than schizophrenia. This paper reviews the evidence documenting the presence of thought, language and communication disorders in schizophrenic patients and in their first-degree relatives. This familial aggregation potentially implicates genetic factors in the etiology of thought disorder, language anomalies, and communication disturbances in schizophrenia families. We also present two examples of ways in which thought, language and communication disorders can enrich genetic studies, including those involving schizophrenia.

Cognitive peculiarities in relatives of schizophrenic and schizoaffective patients: heritability and resting EEG-correlates

The role of genetic factors in liability to schizophrenia is well established. It is supposed that different susceptibility genes produce distinct neurobiological and behavioural phenotypes that may each increase the risk for developing schizophrenia. The aim of the study was to search for genetically and pathophysiologically independent domains of mild cognitive disturbances that might be the components of liability to schizophrenia. One hundred and twenty-seven adult relatives of schizophrenic and schizoaffective patients were tested with a battery of cognitive tasks. Results were subjected to a principal component analysis, and factors obtained were further investigated with behavioural genetic methods in 56 families of schizophrenics. Resting EEGs were recorded from a subsample of 66 relatives. Correlations of the cognitive factors with absolute power values of seven frequency bands at 16 derivations were assessed using regression analysis. The study revealed four components of cognitive deficits in relatives of schizophrenics in domains of verbal short-term memory, thinking, communication and attention/working memory, all with substantive heritability except the last. The four components had a partial overlapping, but still distinct patterns of resting EEG correlates. The findings are in line with the assumption that cognitive deficit in high-risk individuals may be decomposed to relatively independent dimensions, each with its specific genetic and pathophysiological background.