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Formal thought disorder refers to an impaired capacity to sustain coherent discourse, and occurs in the patient’s written or spoken language.
- Whereas delusions reflect abnormal thought content, formal thought disorder indicates a disturbance of the organization and expression of thought.
- Indeed, the most basic assessment of thought content requires at least some degree of language competence.
- For research purposes, scales have been developed to study the quality and severity of abnormalities in thought, language, and communication.
- In clinical practice, formal thought disorder is assessed by engaging patients in open-ended conversation and observing their verbal responses.
- A number of medical and surgical conditions can affect language performance; the term formal thought disorder is used when these conditions are excluded from the diagnosis.
- The cause of formal thought disorder is not established. Research has implicated abnormalities in the semantic system in patients with schizophrenia.
- Thought disorder is often accompanied by executive function problems and general disorganization.
- Abnormalities in language are common in the general population, in everyday conversation. Thus, the categorical presence or absence of the following language problems is not absolutely diagnostic of any condition. However, heightened frequency and severity of these problems should be noted by the physician and accounted for in the patient’s diagnostic formulation.
Formal thought disorder descriptors (adapted from the Thought, Language, and Communication scale) :
- Poverty of speech: restricted quantity of speech. Brief, unelaborated responses
- Poverty of content of speech: adequate speech quantity with prominent vagueness and inappropriate level of abstraction
- Pressure of speech: increased rate and quantity of speech. Speech may be loud and difficult to interrupt
- Distractible speech: topic maintenance difficulties due to distraction by nearby stimulus
- Tangentiality: replies to questions are off-point or totally irrelevant
- Derailment (loosening of associations): spontaneous speech with marked impairments in topic maintenance
- Incoherence (word salad, schizaphasia): severe lack of speech cohesion at the basic level of syntax and/or semantics within sentences
- Illogicality: marked errors in inferential logic
- Clanging: speech in which word choice is governed by word sound rather than meaning. Word choice may show rhyming or punning associations
- Neologism: the creation of new "words"
- Word approximations: unconventional and idiosyncratic word use
- Circumstantiality: excessively indirect speech. Speech is liable to be overinclusive and include irrelevant detail
- Loss of goal: difficulty in topic maintenance in reference to failure to arrive at the implicit goal of a statement
- Perseveration: excessive repetition of words, ideas, or subjects
- Echolalia: speech repeats words or phrases of interviewer
- Blocking: interruption of speech while ostensibly in pursuit of a goal
- Stilted speech: odd language use that may be excessively formal, pompous, oudated or quaint
- Self-reference: the patient is liable to refer the subject of conversation back to him/herself
- Paraphasic error (phonemic): word mispronunciation, slip of the tongue
- Paraphasic error (semantic): substitution of an inappropriate word to make a specific statement