Assessment of Formal Though Disorder

Learn to assess formal thought disorder in a patient with schizophrenia or other psychotic disorder for MRCPsych CASC, or other psychiatry exams.


Formal Thought Disorder in Context

To understand formal thought disorder, lets revise the concepts of form, content and stream of thought.

  • Content

    The content of thought is the subject, the information in the thought. It is of most importance to the patient themselves, may contain clues to diagnosis but helpful for management.

  • Form

    Form of thought is the way people experience or express thoughts, and the way thoughts proceed one after the other irrespective of their quantity. It helps in the diagnosis of psychiatric disorders.

  • Stream

    The stream of thoughts is the "quantity of thoughts." Patients may experience abundance, slowness, poverty of thoughts. Patients are often aware of this and may report it voluntarily.

Disorders of the form of thought

A good understanding of formal thought disorder helps to assess and interpret the findings of your assessment with a patient. Let us quickly revise the disorders of the form of thought.

Schneider Classification

Schneider named five features of formal thought disorder: 

  1. Derailment
  2. Substitution
  3. Omission
  4. Fusion
  5. Driveling. 


Derailment

There is a disordered intermixture of constituent parts of one complex thought. 

Schneider suggested there were three features of healthy thinking: 

Constancy

This is characteristic of a completed thought that does not change in content unless it is superseded by another consciously derived thought.

Organization

The contents of thought are related to each other in consciousness and do not blend with each other but are separated in an organized way.

Continuity:

There is a continuity of the sense continuum, so that even the most heterogeneous subsidiary thoughts, sudden ideas or observations that appear are arranged in order in the whole content of consciousness.

Schneider claimed that individuals with schizophrenia complained of three different disorders of thinking that correspond to these three features of normal or non-disordered thinking. 

Transitory thinking

Transitory thinking is characterized by derailments, substitutions, and omissions. An omission is distinguished from desultory thinking because in desultoriness the continuity is loosened but in omission, the intention itself is interrupted and there is a gap. The grammatical and syntactical structures are both disturbed in transitory thinking.

Driveling thinking

With driveling thinking, the patient has a preliminary outline of a complicated thought with all its necessary details but loses the preliminary organization of the thought, so that all the constituent parts get muddled together. A patient with driveling has a critical attitude towards their thoughts, but these are not organized and the inner material relationships between them become obscured and change significance.

Desultory thinking

In desultory thinking, speech is grammatically correct, but sudden ideas force their way in from time to time.