Thought & Speech › Formal Thought Disorder

Desultory Thinking

Desultory thinking is a form of formal thought disorder in which speech remains grammatically correct throughout, but is repeatedly interrupted by sudden, unconnected ideas forcing their way in. Each intruding idea is, in itself, a simple and reasonable thought — it would be appropriate if it had occurred at the right moment — but its appearance here disrupts the intended flow of thinking.

This has traditionally been described as a breakdown specifically in the normal 'continuity' of thought — the property by which even scattered, subsidiary thoughts and sudden observations are ordinarily still arranged in an orderly relationship to the whole content of consciousness — distinguishing it from a breakdown in constancy or organisation.

Recognition features

• Grammar and sentence structure remain intact throughout, unlike in transitory thinking
• Sudden, self-contained ideas intrude into the flow of speech at points where they do not belong
• Each intruding idea is coherent and would make sense on its own, given a different context
• The overall continuity of the intended train of thought is repeatedly broken by these intrusions

Eliciting it at interview

• Listen for sudden, well-formed but contextually out-of-place remarks breaking into an otherwise coherent account
• Ask the person whether they noticed the interruption and, if so, how they experienced it, since insight into the intrusions can vary
• Distinguish carefully from ordinary tangential remarks by checking whether the person's overall grammar and delivery remain smooth despite the sudden change in content

Distinguishing features

• Differs from transitory thinking specifically in that grammar and syntax remain correct throughout; the disruption is one of content and continuity, not sentence structure
• Differs from omission (a feature of transitory thinking) in that here the continuity is loosened by an added, intact idea rather than being interrupted by an actual gap
• Each intruding idea is internally coherent, distinguishing this from more globally disorganised speech

Common misconceptions

• That desultory thinking is simply distractibility; the grammatically intact but repeatedly interrupted quality of the speech is a more specific finding than ordinary loss of focus
• That every off-topic remark reflects desultory thinking; the hallmark is a pattern of repeated, well-formed but contextually intrusive ideas breaking the continuity of an otherwise connected account

Related phenomena

Formal Thought Disorder · Transitory Thinking

Practice this

A patient's speech remains grammatically correct throughout, but is repeatedly interrupted by sudden, unconnected ideas forcing their way in, each one coherent on its own but disrupting the intended flow of thought. What is this? · A patient begins a sentence describing his weekend, and partway through, without any grammatical break, the sentence itself trails off mid-clause into an entirely unrelated and structurally garbled ending. Before revealing the answer: is this desultory thinking? · A patient's train of thought is repeatedly disrupted mid-course. Before revealing the answer, decide what distinguishes desultory thinking from transitory thinking. · A patient's explanation of a complex idea does not come out coherently. Before revealing the answer, decide what distinguishes drivelling thinking from desultory thinking. · You suspect a patient's speech shows desultory thinking. Before revealing the answer, decide how you would assess for this. · Explain why each intruding idea in desultory thinking is described as being, in itself, a "simple and reasonable thought."

Illustration

While giving a clear, grammatically fluent account of her weekend, a 36-year-old woman suddenly remarks, "the post office closes at five," fully formed and correctly phrased but entirely unconnected to anything she had been saying, before resuming her original account a moment later as though nothing had happened.

References

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