Formal Thought Disorder in Schizophrenia: A Problematic History

Formal thought disorder (FTD), studied even before the inception of the concept of schizophrenia, remains a deeply isolating experience for patients as well as a difficult one for their interlocutors, including clinicians. The views on language, paralinguistic, and extralinguistic features exhibited by patients with severe mental ill health are reviewed, including the contributions from 19th-century European authors to the last third of the 20th century. Stages in the construction of FTD are described, including its merging with Dementia Praecox, and its subsequently being shaped by notions such as primitive archaic thinking, paralogical or autistic thinking, concretism, overinclusive thinking, and the return of the efforts to describing it with increased reliability. It appears that some features of communication in schizophrenia, but not others, have been selected at different points in time for clinical and research use without realizing that by carrying out that selection, the phenomenon under study itself is changed. Remarkably, some theories of FTD remained in use, despite being empirically disproved (eg, word association disorder, concrete thinking, paralogical thinking) or despite its highly problematic and discriminatory nature. We would suggest that studies of FTD should explicitly consider which and why some of its features are included or excluded when assessing it. Furthermore, we would suggest that the study of FTD should incorporate the complexity of human communication, including the pragmatic, paralinguistic, non-verbal, and cognitive dimensions of the localized and unique situation where it takes place.