15th November 2023

What Causes Formal Thought Disorder in Schizophrenia?

There are a variety of different explanations that are present in the literature, and in truth, the cause may be multifactorial.

• Von Domarus’ law – This refers to when a patient’s inductive thoughts become significantly dominant, and they cease to think deductively. The outcome of this is that two things which are similar become confused to be identical. For example, a psychotic man expresses his female romantic partner as his mother because they are both caring and offer him emotional support.
• Impaired semantic memory – Semantic memory is memory associated with words, concepts and numbers. When this is impaired, the links between words and qualities decrease, which can result in formal thought disorder.
• Impaired direct semantic priming – Thinking of certain words brings other words into one’s mind. For example, if one thinks of the word ‘clock’, it triggers thoughts about ‘seconds’, ‘minutes’ or ‘alarm’. Conversely, an example of indirect semantic priming could be that thinking of ‘clock’ activates ‘alarm’, which activates ‘fear’. Indirect semantic priming is increased, which can lead to thoughts becoming scrambled.
• Theory of mind – This is the ability to understand other people’s perspectives and allows us to empathise. Its loss gives rise to concrete thinking, which we will discuss later, but for now, it is associated with some of the pragmatic errors observed in schizophrenia.
• Dysexecutive problems – These arise in the frontal lobe and, if present, cause problems with planning, abstract thinking, cognitive flexibility, working memory and error monitoring during speech production.

The German neurologist and psychiatrist Karl Kleist (1879 – 1960) was key to the development of descriptive psychopathology. He believed that with schizophrenia, it was more commonplace to observe semantic errors in thoughts rather than grammatical or syntactical. This could result in:

• Verbal paraphasia – Where a word is replaced with an inappropriate word or phrase, but the sentence can still be understood. For example: ‘blood pumping muscular device’ instead of ‘heart.’
• Literal paraphasia – Also known as phonemic paraphasia. This is when the pronunciation (i.e. the sound) of the word changes, but again, the word can still be understood based on the context of the sentence. For example: ‘gelevision’ instead of ‘television.’ At least 50% of the word must be pronounced correctly for it to be considered a literal paraphasia.

References

• Prathap, S. (2019). SPMM Smart Revise. SPMM Course.
• Taylor, M., & Vaidya, N (2008). Disturbances in speech and language. In Descriptive Psychopathology: The Signs and Symptoms of Behavioral Disorders (p. 224-252). Cambridge: Cambridge University Press