Thought disorder

Thought disorder
Other names	Formal thought disorder (FTD), thinking disorder
Cloth embroidered by a person diagnosed with schizophrenia; non-linear text has multiple colors of thread.
Specialty	Psychiatry, clinical psychology

A thought disorder (TD) is a disturbance in cognition which affects language, thought and communication.^[1][2] Psychiatric and psychological glossaries in 2015 and 2017 identified thought disorders as encompassing poverty of ideas, neologisms, paralogia (a reasoning disorder characterized by expression of illogical or delusional thoughts), word salad, and delusions—all disturbances of thought content and form. Two specific terms have been suggested—content thought disorder (CTD) and formal thought disorder (FTD). CTD has been defined as a thought disturbance characterized by multiple fragmented delusions, and the term thought disorder is often used to refer to an FTD:^[3] a disruption of the form (or structure) of thought.^[4] Also known as disorganized thinking, FTD results in disorganized speech and is recognized as a major feature of schizophrenia and other psychoses^[5][6] (including mood disorders, dementia, mania, and neurological diseases).^[7][5][8] Disorganized speech leads to an inference of disorganized thought.^[9] Thought disorders include derailment,^[10] pressured speech, poverty of speech, tangentiality, verbigeration, and thought blocking.^[8] One of the first known cases of thought disorders, or specifically OCD as it is known today, was in 1691. John Moore, who was a bishop, had a speech in front of Queen Mary II, about "religious melancholy."^[11]

Formal thought disorder affects the form (rather than of the content) of thought.^[12] Unlike hallucinations and delusions, it is an observable, objective sign of psychosis.^[12] FTD is a common core symptom of a psychotic disorder, and may be seen as a marker of severity and as an indicator of prognosis.^[8][13] It reflects a cluster of cognitive, linguistic, and affective disturbances that have generated research interest in the fields of cognitive neuroscience, neurolinguistics, and psychiatry.^[8]

Eugen Bleuler, who named schizophrenia, said that TD was its defining characteristic.^[14] Disturbances of thinking and speech, such as clanging or echolalia, may also be present in Tourette syndrome;^[15] other symptoms may be found in delirium.^[16] A clinical difference exists between these two groups. Patients with psychoses are less likely to show awareness or concern about disordered thinking, and those with other disorders are aware and concerned about not being able to think clearly.^[17]