In psychiatry, thought disorder or formal thought disorder is a term used to describe a symptom of psychotic mental illness.

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 or punning or 'word salad' when individual words may be intact but speech is incoherent.

Subtypes in detail

Nancy Andreasen¹ 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. "What city are you from ?", "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
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 due to the fact that, 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 believe in God?" elicits a response like "Because make a twirl in life, my box is broken help me blue elephant. Isn't lettuce brave? I like electrons, hello."

Illogicality
Conclusions are reached that do not follow logically (non sequiturs or faulty inductive inferences).

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.

Loss of goal
Failure to show a chain of thought to a natural conclusion.

Perseveration
Persistent repetition of words or ideas. e.g. "I'll think I'll put on my hat, my hat, my hat, my hat, my hat, my hat, my hat, my hat..."

Echolalia
Echoing of other people's speech e.g. "Can we talk for a few minutes?", "Talk for a few minutes".

Blocking
Interruption of train of speech before completed.

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
Mispronounciation; 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".

Diagnostic issues

The concept of thought disorder has been criticised as being based on circular or incoherent definitions². 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.

See also

• psychosis
• schizophrenia

Further Reading

• Sims, A. (1995) Symptoms in the mind: An introduction to descriptive psychopathology. Edinburgh: Elsevier Science Ltd. ISBN 0702026271

References

¹Andreasen NC. (1979) Thought, language, and communication disorders. I. Clinical assessment, definition of terms, and evaluation of their reliability. Archives of General Psychiatry, 36(12), 1315-21.
²Bentall, R. (2003) Madness explained: Psychosis and Human Nature. London: Penguin Books Ltd. ISBN 0713992492