Thought & Speech

Formal Thought Disorder

Formal thought disorder is a disturbance in the structure or organisation of thinking itself, rather than in what is believed. It affects how ideas are put together and expressed, most often in speech, and is best recognised through the way a person's language fails to hold together in its usual logical, connected way, rather than through the content of any particular idea.

This has traditionally been treated as a disorder of reasoning, in contrast to disorders of the content of thinking such as delusions, which are disorders of belief; the boundary between the two is acknowledged to be somewhat artificial, since belief and reasoning cannot always be cleanly separated in practice.

Also known as

Condensation

Two ideas that share something in common are blended together into one false, combined concept.

Displacement

One idea is substituted for another, related idea, in the course of thinking.

Concrete thinking

The literal, surface aspect of a symbol or expression is used in place of its intended, abstract meaning.

Asyndesis

A lack of adequate logical connection between successive thoughts, without the thoughts themselves being individually bizarre.

Over-inclusion

An inability to narrow thinking down to what is relevant to the task at hand, so that irrelevant material keeps being drawn in.

Fusion

Distinct, unrelated elements of thought become interwoven with one another rather than remaining separate.

Recognition features

• Speech or writing that fails to hold together in the ordinarily connected, logical way expected of coherent thought
• Difficulty may show up as blended concepts, substituted ideas, overly literal use of language, or the intrusion of irrelevant material
• Best assessed through spontaneous, relatively unstructured speech rather than through simple yes/no questioning
• Most commonly seen in schizophrenia and in organic brain disorders, and may coexist with other cognitive deficits, complicating assessment

Eliciting it at interview

• Allow a period of relatively free, spontaneous speech, since formal thought disorder is often far more apparent here than in response to closely structured questions
• Listen for whether the connections between successive ideas make ordinary logical sense, rather than focusing only on the plausibility of the content itself
• Ask the person to explain a common proverb or expression, since an overly literal, concrete answer can reveal a loss of abstract thinking

Distinguishing features

• Differs from a disorder of thought content, such as a delusion, in that it concerns the organisation and structure of thinking, not what is believed
• Differs from a disorder of thought tempo, such as flight of ideas, in which individual connections between thoughts usually remain understandable even though the overall direction is lost
• Can be difficult to distinguish from a co-occurring cognitive deficit, particularly in chronic illness, and careful assessment of both together is often needed

Common misconceptions

• That formal thought disorder simply means 'strange' or 'illogical' beliefs; it specifically concerns the structure and organisation of thinking, independent of whether the content itself is bizarre
• That any single odd phrase or word choice indicates thought disorder; a sustained pattern across spontaneous speech is needed before concluding this is present

Related phenomena

Transitory Thinking · Drivelling Thinking · Desultory Thinking · Distractibility · Neologism · Schizophasia

Diagnostically relevant to

Schizophrenia (links open the DSM-5 Learning Lab)

Practice this

During an unstructured conversation, a patient's speech drifts between ideas with connections that are difficult or impossible to follow, blending unrelated concepts together and occasionally using ordinary words in oddly literal ways, making the overall structure of what she is saying hard to grasp even though individual sentences are grammatically intact. What is this? · A patient speaks rapidly and at length, moving quickly from one topic to the next, each new idea clearly triggered by a word or sound from the last, so that a listener can always follow exactly how she got from one thought to the next, even though she never settles on any single topic. Before revealing the answer: is this formal thought disorder? · A patient's speech is difficult to follow. Before revealing the answer, decide what distinguishes formal thought disorder from flight of ideas. · A patient's answers to direct questions are consistently incorrect in an unusual way. Before revealing the answer, decide what distinguishes talking past the point from a formal thought disorder. · You suspect a patient's speech shows a disturbance in the structure of their thinking. Before revealing the answer, decide how you would assess this. · Explain why formal thought disorder is best assessed through spontaneous, unstructured speech rather than structured questioning.

Illustration

Asked to describe her morning, a 30-year-old woman with chronic schizophrenia produces a stream of grammatically correct sentences in which the topic keeps sliding sideways — breakfast becomes an account of birds, which becomes a comment on the texture of the kitchen tiles — with no single thread of logic connecting one sentence convincingly to the next, though each sentence in isolation is perfectly well formed.

References

• Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 4, 'Disorders of Thought and Speech'.