Thought disturbances

Thought disturbances or thought disorder or formal thought disorder is a term used to describe a pattern of disordered language use that is presumed to reflect disordered thinking. It is usually considered a symptom of psychotic mental illness, although it occasionally appears in other conditions.

It describes a persistent underlying disturbance to conscious thought and is classified largely by its effects on speech and writing. Affected persons may show pressure of speech (speaking incessantly and quickly), derailment or flight of ideas (switching topic mid-sentence or inappropriately), thought blocking, rhyming, punning, or 'word salad' when individual words may be intact but speech is incoherent.

Eugen Bleuler, who named schizophrenia, held that its defining characteristic was a disorder of the thinking process. However, the delusions and hallucinations of psychosis could also be considered as disorders of thought, but that the term formal thought disorder applies specifically to the presumed disruption in the flow of conscious verbal thought that is inferred from spoken language. This is typically what is referred to when the strictly less accurate, more commonly used but abbreviated term, 'thought disorder', is used.

Specific subtypes in detail
Nancy C. Andreasen has given the following definitions.
 * Pressure of speech - An increase in the amount of spontaneous speech compared to what is considered customary.
 * Distractible speech - During mid speech, the subject is changed in response to a stimulus. e.g. "Then I left San Francisco and moved to... where did you get that tie?"
 * Tangentiality - Replying to questions in an oblique, tangential or irrelevant manner. e.g:
 * Q: "What city are you from?"
 * A: "Well, that's a hard question. I'm from Iowa. I really don't know where my relatives came from, so I don't know if I'm Irish or French."


 * Derailment/Loose Association (Knight's move thinking) - Ideas slip off the track on to another which is obliquely related or unrelated. 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."
 * 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, 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, beautiful."
 * Illogicality - Conclusions are reached that do not follow logically (non sequiturs or faulty inductive inferences). e.g. "Do you think this will fit in that box?" draws a reply like "Well duh; it's brown, isn’t it?"
 * Clanging - Sounds, rather than meaningful relationships, appear to govern words. e.g. "I'm not trying to make noise. I'm trying to make sense. If you can't make sense out of nonsense, well, have fun."
 * Neologisms - New word formations. e.g. "I got so angry I picked up a dish and threw it at the geshinker."
 * Word approximations - Old words used in a new and unconventional way. e.g. "His boss was a seeover."
 * Circumstantiality - Speech that is very delayed at reaching its goal. Excessive long windedness. e.g. "What is your name?" "Well, sometimes when people ask me that I have to think about whether or not I will answer because some people think it's an odd name even though I don’t really because my mom gave it to me and I think my dad helped but it's as good a name as any in my opinion but yeah it's Tom."
 * Loss of goal - Failure to show a chain 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."
 * Perseveration - Persistent repetition of words or ideas. e.g. "It's great to be here in Nevada, Nevada, Nevada, Nevada, Nevada."
 * Echolalia - Echoing of one's or other people's speech that may only be committed once, or may be continuous in repetition 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."
 * Blocking - Interruption of train of speech before completion. e.g. "Am I early?", "No, you're just about on-"
 * Stilted speech - Speech excessively stilted and formal. e.g. "The attorney comported himself indecorously."
 * Self-reference - Patient repeatedly and inappropriately refers back to self. e.g. "What's the time?", "It's 7 o'clock. That's my problem."
 * Phonemic paraphasia - Mispronunciation; syllables out of sequence. e.g. "I slipped on the lice broke my arm."
 * Semantic paraphasia - Substitution of inappropriate word. e.g. "I slipped on the coat, on the ice I mean, and broke my book."

Diagnosis
The concept of thought disorder has been criticized as being based on circular or incoherent definitions. For example, thought disorder is inferred from disordered speech, however it is assumed that disordered speech arises because of disordered thought. Similarly the definition of 'Incoherence' (word salad) is that speech is incoherent.

Furthermore, although thought disorder is typically associated with psychosis, similar phenomena can appear in different disorders, potentially leading to misdiagnosis.

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 controls. 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.