Thought disorder

Thought disorder (TD) refers to disorganized thinking as evidenced by disorganized speech.[1] Specific thought disorders include derailment, poverty of speech, tangentiality, illogicality, perseveration, and thought blocking.[1] TD is a hallmark feature of schizophrenia, but is also associated with other conditions including mood disorders, dementia, mania, and neurological diseases.[2][3]

Thought disorder
Other namesFormal thought disorder (FTD)
An embroidered cloth produced by a schizophrenia patient, showing the nonsensical associations between words and ideas characteristic of thought disorder

Psychiatrists consider formal thought disorder as being one of two types of disordered thinking, with the other type being delusions. The latter involves "content" while the former involves "form". Although the term "thought disorder" can refer to either type, in common parlance it refers most often to a disorder of thought "form" also known as formal thought disorder.

Eugen Bleuler, who named schizophrenia, held that thought disorder was its defining characteristic.[4] However, formal thought disorder is not unique to schizophrenia or psychosis. It is often a symptom of mania, and less often it can be present in other mental disorders such as depression.[1] Clanging or echolalia may be present in Tourette syndrome.[5] Patients with a clouded consciousness, like that found in delirium, also have a formal thought disorder.[6]

However, there is a clinical difference between these two groups. Those with schizophrenia or psychosis are less likely to demonstrate awareness or concern about the disordered thinking.[7] Clayton and Winokur have suggested that this results from a fundamental inability to use the same type of Aristotelian logic as others.[8] On the other hand, patients with a clouded consciousness, referred to as "organic" patients, usually do demonstrate awareness and concern, and complain about being "confused" or "unable to think straight"; Clayton and Winokur suggest that this is because their thought disorder results, instead, from various cognitive deficits.[6]

Signs and symptoms

In considering whether an individual has thought disorder, patterns of their speech are closely observed. Although it is normal to exhibit some of the following during times of extreme stress (e.g. a cataclysmic event or the middle of a war) it is the degree, frequency, and the resulting functional impairment that leads to the conclusion that the person being observed has a thought disorder.[9][10]

  • Alogia (also poverty of speech) – A poverty of speech, either in amount or content; it can occur as a negative symptom of schizophrenia.[1]
  • Blocking – An abrupt stop in the middle of a train of thought; the individual may or may not be able to continue the idea.[11] This is a type of formal thought disorder that can be seen in schizophrenia.[1]
  • Circumstantiality (also circumstantial thinking, or circumstantial speech) – An inability to answer a question without giving excessive, unnecessary detail.[11] This differs from tangential thinking, in that the person does eventually return to the original point.
  • Clanging or Clang association – a severe form of flight of ideas whereby ideas are related only by similar or rhyming sounds rather than actual meaning.[11] This may be heard as excessive rhyming and/or alliteration. e.g. "Many moldy mushrooms merge out of the mildewy mud on Mondays." "I heard the bell. Well, hell, then I fell." It is most commonly seen in bipolar affective disorder (manic phase), although it is often observed in patients with primary psychoses, namely schizophrenia and schizoaffective disorder.
  • Derailment (also loose association and knight's move thinking) – Thought and/or speech move, either spontaneously or in response to an internal stimulus (distinguishing derailment from "distractible speech," infra), from the topic's track onto another which is obliquely related or unrelated.[11] e.g. "The next day when I'd be going out you know, I took control, like uh, I put bleach on my hair in California."
  • Distractible speech – During mid speech, the subject is changed in response to an external stimulus. e.g. "Then I left San Francisco and moved to... where did you get that tie?"
  • Echolalia – Echoing of another's speech[11] that may only be committed once, or may be continuous in repetition. This may involve repeating only the last few words or last word of the examiner's sentences. This can be a symptom of Tourette's Syndrome. e.g. "What would you like for dinner?", "That's a good question. That's a good question. That's a good question. That's a good question."
  • Evasion - the next logical idea in a sequence is replaced with another idea closely but not accurately or appropriately related to it. Also called paralogia and perverted logic.[12][13] Example: "I... er ah... you are uh... I think you have... uh-- acceptable erm... uh... hair."
  • Flight of ideas - a form of formal thought disorder marked by abrupt leaps from one topic to another, possibly with discernable links between successive ideas, perhaps governed by similarities between subjects or, in somewhat higher grades, by rhyming, puns, and word plays, or by innocuous environmental stimuli – e.g., the sound of birds chirping. It is most characteristic of the manic phase of bipolar illness.[11]
  • Illogicality – Conclusions are reached that do not follow logically (non-sequiturs or faulty inferences). e.g. "Do you think this will fit in the box?" draws a reply like "Well duh; it's brown, isn't it?"
  • Incoherence (word salad) – Speech that is unintelligible because, though the individual words are real words, the manner in which they are strung together results in incoherent gibberish,[11] e.g. the question "Why do people comb their hair?" elicits a response like "Because it makes a twirl in life, my box is broken help me blue elephant. Isn't lettuce brave? I like electrons, hello please!"
  • Loss of goal – Failure to follow a train of thought to a natural conclusion. e.g. "Why does my computer keep crashing?", "Well, you live in a stucco house, so the pair of scissors needs to be in another drawer."
  • Neologisms – New word formations.[11] These may also involve elisions of two words that are similar in meaning or in sound. e.g. "I got so angry I picked up a dish and threw it at the geshinker."
  • Perseveration – Persistent repetition of words or ideas even when another person attempts to change the topic.[11] e.g. "It's great to be here in Nevada, Nevada, Nevada, Nevada, Nevada." This may also involve repeatedly giving the same answer to different questions. e.g. "Is your name Mary?" "Yes." "Are you in the hospital?" "Yes." "Are you a table?" "Yes." Perseveration can include palilalia and logoclonia, and can be an indication of organic brain disease such as Parkinson's.
  • Phonemic paraphasia – Mispronunciation; syllables out of sequence. e.g. "I slipped on the lice and broke my arm."
  • Pressure of speech – Unrelenting, rapid speech without pauses.[11] It may be difficult to interrupt the speaker, and the speaker may continue speaking even when a direct question is asked.
  • Self mentions – Patient repeatedly and inappropriately refers back to self. e.g. "What's the time?", "It's 7 o'clock. That's my problem."
  • Semantic paraphasia – Substitution of inappropriate word. e.g. "I slipped on the coat, on the ice I mean, and broke my book."
  • Stilted speech – Speech characterized by the use of words or phrases that are flowery, excessive, and pompous.[11] e.g. "The attorney comported himself indecorously."
  • Tangentiality – Wandering from the topic and never returning to it or providing the information requested.[11] e.g. in answer to the question "Where are you from?", a response "My dog is from England. They have good fish and chips there. Fish breathe through gills."
  • Word approximations – Old words used in a new and unconventional way. e.g. "His boss was a seeover."

Word Usage

Thought Disorder

Some recent (2015, 2017) pyschiatric/psychological glossaries defined thought disorder as disturbed thinking or cognition that affects communication, language, or thought content including poverty of ideas, neologisms, paralogia, word salad, and delusions[2][3] which are disturbance of both thought content and thought formand suggested the more specific terms of content thought disorder and formal thought disorder,[3] with content thought disorder defined as a thought disturbance characterized by multiple fragmented delusions,[14][15] and formal thought disorder defined as disturbance in the form or structure of thinking.[16][17] For example, DSM-5 (2013) only used the word formal thought disorder, mostly as a synonym of "disorgnized thinking (speech)".[18] This is in contrast with ICD-10 (1992) which only used the word "thought disorder", always accompanied with "delusion" and "hallucination" separately,[19] and a general medical dictionary (2002) that although generally defined thought disorders similarly to the psychiatric glossaries,[20] but also used the word in other entries as ICD-10 did.[21]

The recent psychiatric text (2017) also mentioned when describing thought disorder as a "disorganization syndrome" within the context of schizophrenia:

“Thought disorder” here refers to disorganization of the form of thought and not content. An older use of the term “thought disorder” included the phenomena of delusions and sometimes hallucinations, but this is confusing and ignores the clear differences in the relationships between symptoms that have become apparent over the past 30 years. Delusions and hallucinations should be identified as psychotic symptoms, and thought disorder should be taken to mean formal thought disorders or a disorder of verbal cognition.

Phenomenology of Schizophrenia (2017), THE SYMPTOMS OF SCHIZOPHRENIA[22]

The same text also mentioned that some clinicians use the term "formal thought disorder" broadly referring to abnormalities in thought form plus any psychotic cognitive sign or symptom,[23] and that various studies examining cognition and subsymdromes in schizophrenia may refer to formal thought disorder as "conceptual disorganization" or "disorganization factor."[22]


Alogia, both poverty of speech and poverty of content of speech, had been considered as a "negative symptom" of schizophrenia (for example, see SANS),[24] and was conceived as "negative thought disorder".[25] Factor analysis studies have been classifying negative and positive symptoms of schizophrenia into more dimensions, starting with 3, currently (2017) with 5psychotic symptoms, negative symptoms, disorganization symptoms (including TD), depression and anxiety, agitationwith "remarkable consistency", and expecting more in the future.[26] With such classifications, poverty of content of speech, i.e. paucity of meaningful content with normal amount of speech, is considered "a disorganization of thought and not a negative symptom and is properly included in the disorganization cluster of symptoms." Only poverty of speech, i.e. loss of speech production, is considered a negative symptom.[25]

Thought form, content and process

Disorders of thought form

The most common thought form disorders are: circumstantiality, derailment, flight of ideas, illogicality, incoherence, loose associations, perseveration, tangentiality.[27]

Disorders of thought content

The most common disorders of thought content are delusions of various types (e.g. persecutory, grandiose, referential).[28]

Derealization and depersonalization are another type of abnormal thought content that refer to dissociative experiences.[27]

Intrusive thoughts also are examples of altered thought content. The patient experience involuntary obsessional thoughts, images, or unpleasant ideas that are egodystonic.[27]


The concept of thought disorder has been criticized as being based on circular or incoherent definitions.[29] For example, thought disorder is inferred from disordered speech, based on the assumption that disordered speech arises because of disordered thought. Incoherence, or word salad, refers to speech that is unconnected and conveys no meaning to the listener.[11]

Furthermore, although thought disorder is typically associated with psychosis, similar phenomena can appear in different disorders, potentially leading to misdiagnosis—for example, in the case of incomplete yet potentially fruitful thought processes.

It has been suggested that individuals with autism spectrum disorders (ASD) display language disturbances like those found in schizophrenia; a 2008 study found that children and adolescents with ASD showed significantly more illogical thinking and loose associations than control subjects. The illogical thinking was related to cognitive functioning and executive control; the loose associations were related to communication symptoms and to parent reports of stress and anxiety.[30]

See also


  1. Yudofsky, Stuart C.; Hales, Robert E. (2002). The American Psychiatric Publishing Textbook of Clinical Psychiatry. Washington, DC: American Psychiatric Association. ISBN 1-58562-032-7. OCLC 49576699.
  2. Kaplan and Sadock's Comprehensive Textbook of Psychiatry (2017), "Appendix B: Glossary of Psychiatry and Psychology Terms" "thought disorder Any disturbance of thinking that affects language, communication, or thought content; the hallmark feature of schizophrenia. Manifestations range from simple blocking and mild circumstantiality to profound loosening of associations, incoherence, and delusions; characterized by a failure to follow semantic and syntactic rules that is inconsistent with the person’s education, intelligence, or cultural background."
  3. APA dictionary of psychology (2015), p. 1086 "thought disorder a cognitive disturbance that affects communication, language, or thought content, including poverty of ideas, neologisms, paralogia, word salad, and delusions. A thought disorder is considered by some to be the most important mark of schizophrenia (see also schizophrenic thinking), but it is also associated with mood disorders, dementia, mania, and neurological diseases (among other conditions). Also called thought disturbance. See content thought disorder; formal thought disorder."
  4. Colman, A. M. (2001) Oxford Dictionary of Psychology, Oxford University Press. ISBN 0-19-860761-X
  5. Barrera A, McKenna PJ, Berrios GE (2009). "Formal thought disorder, neuropsychology and insight in schizophrenia". Psychopathology. 42 (4): 264–9. doi:10.1159/000224150. PMID 19521143.
  6. John Noble; Harry L. Greene (15 January 1996). Textbook of primary care medicine. Mosby. p. 1325. ISBN 978-0-8016-7841-7.
  7. Jefferson, James W.; Moore, David Scott (2004). Handbook of medical psychiatry. Elsevier Mosby. p. 131. ISBN 0-323-02911-6.
  8. Clayton, Paula J.; Winokur, George (1994). The Medical basis of psychiatry. Philadelphia: Saunders. pp. 13–14. ISBN 0-7216-6484-9.
  9. Andreasen NC. Thought, language, and communication disorders. I. A Clinical assessment, definition of terms, and evaluation of their reliability. Archives of General Psychiatry 1979;36(12):1315–21. PMID 496551.
  10. Sadock, B.J. and Sadock, V.A. Kaplan and Sadock's Synopsis of Psychiatry. 9th ed. 2003: Table 7.1–6 p 239.
  11. Videbeck, S (2008). Psychiatric-Mental Health Nursing, 4th ed. Philadelphia: Wolters Kluwers Health, Lippincott Williams & Wilkins.
  12. APA dictionary of psychology (2015), p. 389 evasion n. 1. a form of paralogia in which an idea that is logically next in a chain of thought is replaced by another idea closely but not accurately or appropriately related to it. 2. elusion or avoidance.
  13. Kaplan & Sadock's Comprehensive Textbook of Psychiatry (2017), Appendix B Glossary of Psychiatry and Psychology Terms evasion ... consists of suppressing an idea that is next in a thought series and replacing it with another idea closely related to it. Also called paralogia; perverted logic.
  14. Kaplan and Sadock's Comprehensive Textbook of Psychiatry (2017), "Appendix B: Glossary of Psychiatry and Psychology Terms" "content thought disorder Disturbance in thinking in which a person exhibits delusions that may be multiple, fragmented, and bizarre."
  15. APA dictionary of psychology (2015), p. 242 "content-thought disorder a type of thought disturbance, typically found in schizophrenia and some other mental disorders (e.g., obsessive-compulsive disorder, mania), characterized by multiple fragmented delusions."
  16. Kaplan and Sadock's Comprehensive Textbook of Psychiatry (2017), "Appendix B: Glossary of Psychiatry and Psychology Terms" "formal thought disorder Disturbance in the form of thought rather than the content of thought; thinking characterized by loosened associations, neologisms, and illogical constructs; thought process is disordered, and the person is defined as psychotic. Characteristic of schizophrenia."
  17. APA dictionary of psychology (2015), p. 432 "formal thought disorder disruptions in the form or structure of thinking. Examples include derailment and tangentiality. It is distinct from thought disorder, in which the disturbance relates to thought content."
  18. American Psychiatry Association (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington: American Psychiatric Publishing. ISBN 978-0-89042-555-8.
    • As the proper formal thought disorder: "Schizophrenia Spectrum and Other Psychotic Disorders", Key Features That Define the Psychotic Disorders, Disorganized Thinking (Speech), p. 88 "Disorganized thinking (formal thought disorder) is typically inferred from the individual’s speech. ..."
    • As possibly something else: "Dissociative Disorders", Differential Diagnosis, Psychotic disorders, p. 296 "... Dissociative experiences of identity fragmentation or possession, and of perceived loss of control over thoughts, feelings, impulses, and acts, may be confused with signs of formal thought disorder, such as thought insertion or withdrawal. ..."
  19. "The ICD-10 Classification of Mental and Behavioural Disorders: Clinical descriptions and diagnostic guidelines (CDDG)" (PDF). World Health Organization. 1992. Archived (PDF) from the original on 17 October 2004.
    • F06.2 Organic delusional [schizophrenia-like] disorder, p.59: Features suggestive of schizophrenia, such as bizarre delusions, hallucinations, or thought disorder, may also be present. ... Diagnostic guidelines ... Hallucinations, thought disorder, or isolated catatonic phenomena may be present. ...
    • F20.0 Paranoid schizophrenia, p. 80: ... Thought disorder may be obvious in acute states, but if so it does not prevent the typical delusions or hallucinations from being described clearly. ...
    • F20.1 Hebephrenic schizophrenia, p. 81: ... In addition, disturbances of affect and volition, and thought disorder are usually prominent. Hallucinations and delusions may be present but are not usually prominent. ...
  20. The British Medical Association Illustrated Medical Dictionary. Dorling Kindersley. 2002. p. 547. ISBN 0-7513-3383-2. thought disorders Abnormalities in the structure or content of thought, as reflected in a person’s speech, writing, or behaviour. ...
  21. The BMA Illustrated Medical Dictionary (2002)
    • p. 470 psychosis: ... Symptoms include delusions, hallucinations, thought disorders, loss of affect, mania, and depression. ...
    • p. 499-500 schizophrenia: ... The main symptoms are various forms of delusions such as those of persecution (which are typical of paranoid schizophrenia); hallucinations, which are usually auditory (hearing voices), but which may also be visual or tactile; and thought disorder, leading to impaired concentration and thought processes. ...
  22. Lewis, Stephen F; Escalona, Rodrigo; Keith, Samuel J (2017). "12.2 Phenomenology of Schizophrenia". In Sadock, Virginia A; Sadock, Benjamin J; Ruiz, Pedro (eds.). Kaplan & Sadock's Comprehensive Textbook of Psychiatry (10th ed.). Wolters Kluwer. THE SYMPTOMS OF SCHIZOPHRENIA, Disorganization, Thought Disorder. ISBN 978-1-4511-0047-1.
    • As quoted in the templated quote.
    • "Thought disorder is the most studied form of the disorganization symptoms. It is referred to as “formal thought disorder,” or “conceptual disorganization,” or as the “disorganization factor” in various studies that examine cognition or subsyndromes in schizophrenia. ..."
  23. Kaplan and Sadock's Comprehensive Textbook of Psychiatry (2017), "8 Clinical Manifestations of Psychiatric Disorders", Flow and Form Disturbances "Although formal thought disorder typically refers to marked abnormalities in the form and flow or connectivity of thought, some clinicians use the term broadly to include any psychotic cognitive sign or symptom."
  24. Kaplan and Sadock's Concise Textbook of Clinical Psychiatry (2008), "6 Psychiatric Rating Scales", Table 6–5 Scale for the Assessment of Negative Symptoms (SANS), p. 44
  25. Phenomenology of Schizophrenia (2017), THE SYMPTOMS OF SCHIZOPHRENIA, Categories of Negative Symptoms
    • "... In this way, alogia is conceived of as a “negative thought disorder.” ..."
    • "... The paucity of meaningful content in the presence of a normal amount of speech that is sometimes included in alogia is actually a disorganization of thought and not a negative symptom and is properly included in the disorganization cluster of symptoms. ..."
  26. Phenomenology of Schizophrenia (2017), THE SYMPTOMS OF SCHIZOPHRENIA
    • "... By the mid-1980s, factor analytic techniques were being more broadly applied to the assessment of the symptoms of schizophrenia, and separate investigators found that three dimensions or subsyndromes of schizophrenia could be derived from rating scales. ... "
    • "... Scales or combinations of scales that include more diverse examples of psychopathology lead to the reliable derivation of psychotic, negative, disorganization, depression and anxiety, and agitation dimensions. ..."
    • "... there has been a remarkable consistency in the finding of these same five factors. ..."
    • "... This dissection of the syndrome of schizophrenia into subsyndromes will multiply if more and more elaborate assessments of signs, symptoms, and history are completed. ..."
  27. Chow, Tiffany W.; Cummings, Jeffrey L. "Neuropsychiatry: Clinical Assessment and Approach to Diagnosis". In Sadock, Benjamin J.; Sadock, Virginia A. (eds.). Kaplan & Sadock's Comprehensive Textbook of Psychiatry (7th. ed.). Lippincott Williams & Wilkins Publishers.
  28. S. Hossein Fatemi; Paula J. Clayton (15 May 2008). The Medical Basis of Psychiatry. Springer Science & Business Media. pp. 435–436. ISBN 978-1-59745-252-6.
  29. Bentall, R. (2003) Madness explained: Psychosis and Human Nature. London: Penguin Books Ltd. ISBN 0-7139-9249-2
  30. Solomon M, Ozonoff S, Carter C, Caplan R (2008). "Formal thought disorder and the autism spectrum: relationship with symptoms, executive control, and anxiety". J Autism Dev Disord. 38 (8): 1474–84. doi:10.1007/s10803-007-0526-6. PMC 5519298. PMID 18297385.

Other references

  • VandenBos, Gary R, ed. (2015). APA dictionary of psychology (2nd ed.). Washington, DC: American Psychological Association. doi:10.1037/14646-000. ISBN 978-1-4338-1944-5.
  • Sadock, Virginia A; Sadock, Benjamin J; Ruiz, Pedro, eds. (2017). Kaplan & Sadock's Comprehensive Textbook of Psychiatry (10th ed.). Wolters Kluwer. ISBN 978-1-4511-0047-1.
  • Sadock, B. J.; Sadock, VA (2008). Kaplan and Sadock's Concise Textbook of Clinical Psychiatry. Lippincott Williams & Wilkins. ISBN 9780781787468.

Further reading

  • Peter J. McKenna; Tomasina M. Oh (2005). Schizophrenic Speech: Making Sense of Bathroots and Ponds that Fall in Doorways. Cambridge University Press. ISBN 978-0-521-81075-3.

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