Stability of Thought Disorder Index among high-risk and low-risk adoptees in the Finnish adoptive family study of schizophrenia

Dissecting the neurobiology of linguistic disorganisation and impoverishment in schizophrenia

Schizophrenia provides a quintessential disease model of how disturbances in the molecular mechanisms of neurodevelopment lead to disruptions in the emergence of cognition. The central and often persistent feature of this illness is the disorganisation and impoverishment of language and related expressive behaviours. Though clinically more prominent, the periodic perceptual distortions characterised as psychosis are non-specific and often episodic. While several insights into psychosis have been gained based on study of the dopaminergic system, the mechanistic basis of linguistic disorganisation and impoverishment is still elusive. Key findings from cellular to systems-level studies highlight the role of ubiquitous, inhibitory processes in language production. Dysregulation of these processes at critical time periods, in key brain areas, provides a surprisingly parsimonious account of linguistic disorganisation and impoverishment in schizophrenia. This review links the notion of excitatory/inhibitory (E/I) imbalance at cortical microcircuits to the expression of language behaviour characteristic of schizophrenia, through the building blocks of neurochemistry, neurophysiology, and neurocognition.

Parental communication and psychosis: a meta-analysis

BACKGROUND

Parental communication deviance (CD) has long been suggested as a potential risk factor for the development of psychosis and thought disorder in genetically sensitive offspring. However, the findings of the studies on the prevalence of CD in parents of psychotic patients have never been submitted to quantitative synthesis.

METHOD

PsycINFO was searched from January 1959 to January 2012 for studies on the prevalence of CD in parents of psychotic patients. This search was supplemented with the results from a much larger systematic search (PsycINFO, PubMed, EMBASE, and Web of Science) on childhood trauma and psychosis.

RESULTS

A total of 20 retrieved studies (n = 1753 parents) yielded a pooled g of large magnitude (0.97; 95% CI [0.76; 1.18]) with a significant amount of heterogeneity (Q = 33.63; P = .014; I (2) = 46.47). Subgroup and sensitivity analysis of methodological features (study's design, comparison group, diagnostic criteria, CD rating method, inter-rater reliability not reported, year of publication, and verbosity) and demographic characteristics (level of education or offspring's age) revealed that pooled effect size was stable and unlikely to have been affected by these features.

CONCLUSION

CD is highly prevalent in parents of psychotic offspring. This is discussed in the broader context of adoption and longitudinal studies that have reported a G × E interaction in the development of psychosis and thought disorder. A potential developmental mechanism is suggested to explain how CD may affect the developing offspring. The importance of further studies on CD and its potential value as a clinical concept are discussed.

The stability of severe thought disorders and mature thinking

The aim of this study was to investigate whether severe formal thought disorders and mature thinking are stable among adoptees (=187) drawn from the Finnish adoptive family study of schizophrenia. A group of 93 adoptees genetically at high risk (HR) and 94 at low risk (LR) for schizophrenia were assessed blindly and reliably using the Index of Primitive Thought (IPT) and the Index of Integration (IOI). Two assessments of the IPT and the IOI were performed with the mean interval of 11 years. Comparisons of the IPT and the IOI mean scores were conducted both at baseline and at follow-up between adoptees at low and high genetic risk, gender, and psychiatric status. The main result was that the IOI as well as the IPT of the adoptees at the initial assessment predicted the IOI and the IPT estimated at follow-up, thus indicating the stability of severe formal thought disorders and mature thinking over time. The stability of IOI or IPT was not related to genetic risk, gender or psychiatric status or their interactions.

Differentiating adolescents at clinical high risk for psychosis from psychotic and non-psychotic patients with the Rorschach

This study was designed to assess cognitive functioning in a clinical sample of adolescents with heterogeneous psychiatric diagnoses, with a specific focus on patients at clinical high risk (CHR) for psychosis. The sample comprised 22 patients identified at CHR for psychosis, 67 psychotic and 187 non-psychotic, non-CHR patients. Neuropsychological assessment was conducted as part of the clinical examination and treatment, including Wechsler Intelligence Scale for Children (WISC)-III and/or Wechsler Adult Intelligence Scale (WAIS)-III measures of verbal comprehension, perceptual organisation, working memory and processing speed, Wisconsin Card Sorting Test (WCST) measures of executive function, and the Rorschach Comprehensive System measures of perceptual and thinking accuracy. Patients at CHR for psychosis did not significantly differ from other patient groups in terms of intellectual or executive functions. The Rorschach Perceptual Thinking Index (PTI) distinguished patients at CHR for psychosis from those diagnosed as having non-psychotic disorders, but not from those diagnosed as psychotic. Our results suggest perceptual and thought disturbance as an important indicator of vulnerability to psychosis.

Thought Disorder Index: a longitudinal study of severity levels and schizophrenia factors

BACKGROUND

Thought disturbances are commonly associated with psychiatric disorders, especially schizophrenia. Our aim was to clarify whether thought disorders are only stable at certain severity levels and in the presence of certain schizophrenia factors of the Thought Disorder Index (TDI) scale. Furthermore, we also examined the significance of genetic status and the psychiatric disorder for the persistence of TDI severity levels and factors.

METHODS

The thought disorders of 158 adoptees genetically at high-risk or low-risk for schizophrenia participating the Finnish Adoptive Family Study of Schizophrenia were evaluated twice at a mean interval of 11 years. Thought Disorder Index (TDI) was used to assess the severity levels and schizophrenia factors. TDI identifies 23 different items of thinking disturbances, which are weighted along a continuum of severity.

RESULTS

Thought disorders at the 0.50 and 0.75 severity levels and idiosyncratic verbalization indicative of the schizophrenia factors turned out to be stable phenomena throughout the follow-up period. The adoptees' genetic or psychiatric status was not associated with the results.

CONCLUSIONS

The study shows that the stability of TDI seems to be related to the most severe categories of thought disorders. However, of the specific schizophrenia factors, idiosyncratic verbalization, but not confusion and fluid thinking, showed stability over time. Although idiosyncratic verbalization does not necessarily represent the most severe type of thought disturbance, it turned out relatively stable and we can speculate that idiosyncratic verbalization have some predictive value, too.