A patient shifts from one topic to another with no apparent connection between the topics. Which term best describes this phenomenon?
Thought disorder
Disorders of the form of thoughts (rather than content) are best observed from the patient's speech. A lack of an adequate connection between two consecutive thoughts is called asyndesis.
Thought disorder includes:-
- Disturbances in the flow of thoughts
- Over inclusive thinking
- Concrete and abstract thinking
- Disorders of control of thinking
Disorders of the flow of thoughts include:-
Changes in speed. Thoughts can be accelerated or slowed down (retarded). Very rapid thinking is described as flight of ideas. In flight of ideas the speech is usually (but not always) fast. There is no general direction of thinking and the content of the speech makes as much sense if read backwards as it does forwards. Successive thoughts appear to be connected due to chance leading to clang associations, proverbs, maxims, and clichés.
It is usually seen in mania but also occurs in schizophrenia and organic states such as those involving lesions of the hypothalamus (hence it is not pathognomic of mania).
Prolixity refers to a marginal variety of flight of ideas seen in hypomania where clang and verbal associations are less frequent, there is a general direction of thought and it is not as rapid.
Circumstantiality. Patients are unable to answer concisely. Instead they must consider in detail any association that comes to mind. This is generally seen in organic states and mental retardation. It can also occur in obsessional personality.
Perseveration. This is the inability to shift from one theme to another.
Interruptions to the flow of thoughts. These include thought block which is a sudden cessation in the flow of thoughts and loosening of association, which refers to a deviation towards unrelated thoughts. Loosening of association includes tangentiality, fusion, and derailment. In tangentiality the thoughts shift to vaguely related themes whereas in derailment there is no apparent connection between themes.
Crowding of thought This occurs in schizophrenia. Thoughts are described as being passively concentrated and compressed in the patient's head. The associations are experienced as being excessive in amount, too fast, and outside the person's control.
