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

The aim of the study was to evaluate whether thought disorders are stable, trait-like features specific to subjects who have a genetic liability to schizophrenia or a psychiatric disorder. The thought disorders of adoptees genetically at high risk (HR) or low risk (LR) for schizophrenia from the Finnish adoptive family study of schizophrenia were evaluated twice at a mean interval of 11 years, using the sum of the Thought Disorder Index (TDI) scores on the Rorschach (TDR). At the initial assessment, the mean TDR scores of women were significantly higher than those of men, while no association between genetic risk and psychiatric status or their interactions with the TDR scores at baseline were found. The main finding was that the initial TDR scores statistically significantly predicted the TDR scores at follow-up, thus indicating the stability of thought disorder over time. However, neither genetic or psychiatric status nor gender or any interaction between these variables associated with TDR at follow-up.