Thought is the ability to generate a goal-oriented, logical sequence of impressions, ideas, symbols and associations that result from a problem or task, and which leads to a conclusion based on reality. Thought is therefore an internal process, to be distinguished by form and content.
Formal Thought Disturbance: The formal process of thinking is characterised by normal speed and a normal sequence of associations between thoughts that are experienced as coherent and logical.
- A dysfunction in this formal process may be observed during the anamnesis, but may also be subjective and should be checked with the patient:
- Inhibited (delayed) thought implies that the patient experiences their speed of thinking as slow or halting. In such cases, the physician will observe delayed responses to questions; the patient may pause or even stop responding entirely. This inhibited or delayed thought process is characteristic of a depressive disorder, but may also occur in expressive phatic disorders, such as dementia, when the patient speaks in telegrams and has difficulty finding words. A delayed or halting thought process may also be indicative of the negative symptoms of schizophrenia. The patient’s thought process may appear slow, but on further exploration, the patient reports to subjectively possess a normal speed of thought but feels forced to consider a huge number of options before they can express themselves. This may reflect a highly nuanced way of thinking, but is also indicative of OCD.
-
- Pressured (racing) thought implies that the patient feels pressurised by a large number of insights or recurrent thoughts in rapid succession. This is usually accompanied by tachylalia (accelerated speech) and logorrhoea (word flux).
-
- Circumstantial thought indicates that the patient lacks ability to distinguish major from minor issues, so they get lost in detail. This is indicative of non-psychiatric disorders such as epilepsy, but also of compulsions associated with e.g. OCD.
-
- Derailed thought (also Loose Association/Knight’s Move thinking) implies that the patient is unable to keep track of normal associative thought sequences. This loss may manifest itself in an increased associative thinking (flight of ideas), whereby the stream of thought frequently changes content through new associations, such as sound associations (clanging). This loose form of successive thoughts becomes clear on further investigation or in the course of recording the anamnesis. Derailed thought is indicative of mania, but also of non-psychiatric disorders such as epilepsy. This loss of normal associative thought sequences may take such a form that all coherence is lost and the patient is no longer comprehensible, not even after a request for clarification. This incoherence is a indication of schizophrenia, mania, but also of non-psychiatric disorders such as epilepsy and receptive phatic disturbances.
-
- Concrete thinking (concretism) implies that the patient prefers to give a literal meaning to an abstract cognitive concept. This may be indicative of schizophrenia or mental retardation.
Though Content Disturbance: The physician may observe that a patient is uncomfortable about certain matters, and this concern is decisive for the contents of the patient’s thoughts.
- Dysfunctions in the content of thought are ultimately determined by exploring the thought-contents of the patient:
- Poverty of thought implies that the patient has few ideas, or clings to a limited number of topics. This poverty of thought is often accompanied by a reduction in speech output and is indicative of a depressive disorder, schizophrenia (indication of the negative symptom cluster), autism, and advanced stages of dementia.
-
- Preoccupation implies that the patient is unduly occupied by a limited set of thoughts. Preoccupation is indicative of anxiety disorders, trauma, stress disorders, depressive disorders, somatoform disorder, paraphilia, schizophrenia and eating disorders.
-
- Obsession implies that the patient is entirely occupied by a limited set of thought and is guided by them, without loss of sense of reality. A patient who suffers from an obsession experiences his obsessive thoughts as intrusive and can only with the greatest of efforts block these thoughts. These thoughts are almost always disturbing, in particular since the patient experiences them as an infringement on his autonomy. Obsessions are a characteristic sign of OCD, whereby a fear of something or someone absorbs the patient entirely, and are accompanied by particular acts (compulsions) to neutralise them.
-
- Rumination implies that the patient constantly reconsiders and ponders over bad feelings, experiences and problems from the past, real or imaginary, without ever reaching a solution. Worrying implies that a patient is concerned over potential relevant events in the future. Rumination is indicative of a depressive disorder or a post-traumatic stress disorder.
-
- Ideas of reference suggest that the patient has the belief or perception that irrelevant, unrelated or innocuous phenomena in the world refer to them directly or have special personal significance, when they do not. In case of referential ideas, the patient is still open to correction.
-
- Delusional perceptions imply that the patient is attributing a false mystical meaning or a sense of threat to an otherwise correct perception.
-
- Delusions imply that the patient has a belief which conflicts with the patient’s cultural context, intelligence and social background and is held with unshakeable conviction, despite sufficient or conclusive evidence to the contrary. Almost all delusions are essentially delusions of reference, since the content of a delusion is an inaccurate and often illogical conviction of the relationship that the patient maintains with the outside world.
- Delusions are further classified according to their content:
- Paranoid delusions include erotomania, grandiose delusions, religious delusions, delusions of immortality and paranormal delusions.
-
- Delusions related to depression (delusions of guilt, sin, poverty or apocalyptic delusions) and somatic delusions (denial that one has a physical body or organ or the conviction that one’s body is decomposing). Somatic delusions do not require a nihilistic content, but can be of a sexual or dysmorphic nature (claims to have a disfiguring physical defect).
-
- Delusional misidentification (Capgras delusion) sustains the incorrigible belief that a person close to them has been replaced by an identical-looking impostor.
-
- Delusions that influence the thought process itself are known as passivity delusions. The patient holds the unshakeable conviction to have lost control over their own thoughts. Thought insertion, the belief that thoughts have been implanted in the patient’s mind by some outside agent. Thought obstruction/expansion, thoughts are shared with others, and therefore belong to other people too. Thought broadcasting, thoughts are audible to everyone. Mind reading, others can read the patient’s thoughts.
Delusions are a characteristic sign of psychotic disorders (schizophrenia and related disorders), but also of a psychotic depression, delirium, dementia and non-psychiatric disorders, including epilepsy and fronto-temporal brain disorders.
