Thought disorder
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]
Thought disorder
Formal thought disorder (FTD), thinking disorder
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]
Content thought disorder is a thought disturbance in which a person experiences multiple, fragmented delusions, typically a feature of schizophrenia and some other mental disorders which include obsessive-compulsive disorder and mania.[18][19] At the core of thought content disorder are abnormal beliefs and convictions (after taking the person's culture and background into consideration) ranging from overvalued ideas to fixed delusions.[20] These beliefs and delusions are typically non-specific diagnostically,[21] even if some delusions are more prevalent in one disorder than another.[22]
Neurotypical thought—consisting of awareness, concerns, beliefs, preoccupations, wishes, fantasies, imagination, and concepts—can be illogical, and can contain contradictory beliefs and prejudices or biases.[23][24] Individuals vary considerably, and a person's thinking may also shift from time to time.[25]
Content thought disorder is not limited to delusions. Other possible abnormalities include suicidal, violent, and homicidal ideas[26] and:[27][20]
In psychosis, delusions are the most common thought content disorder.[30] A delusion is a firm, fixed belief based on inadequate grounds, not amenable to rational argument or evidence to the contrary, which is out of sync with a person's regional, cultural, or educational background.[31] Delusions are common in people with mania, depression, schizoaffective disorder, delirium, dementia, substance use disorders, schizophrenia, and delusional disorders.[21] Common examples in a mental status examination include the following:[28]
Criticism[edit]
TD has been criticized as being based on circular or incoherent definitions.[110] Symptoms of TD are inferred from disordered speech, based on the assumption that disordered speech arises from disordered thought. Although TD is typically associated with psychosis, similar phenomena can appear in different disorders and leading to misdiagnosis.[111]
A criticism related to the separation of symptoms of schizophrenia into negative or positive symptoms, including TD, is that it oversimplifies the complexity of TD and its relationship to other positive symptoms.[112] Factor analysis has found that negative symptoms tend to correlate with one another, but positive symptoms tend to separate into two groups.[112] The three clusters became known as negative symptoms, psychotic symptoms, and disorganization symptoms.[99] Alogia, a TD traditionally classified as a negative symptom, can be separated into two types: poverty of speech content (a disorganization symptom) and poverty of speech, response latency, and thought blocking (negative symptoms).[113]
Positive-negative-symptom diametrics, however, may enable a more accurate characterization of schizophrenia.[114]