Thought disorder

A thought disorder (TD) is a multifaceted construct that reflects abnormalities in thinking, language, and communication. Thought disorders encompass a range of thought and language difficulties and include poverty of ideas, perverted logic (illogical or delusional thoughts), word salad, delusions, derailment, pressured speech, poverty of speech, tangentiality, verbigeration, and thought blocking. One of the first known public presentations of a thought disorder, specifically obsessive–compulsive disorder (OCD) as it is now known, was in 1691, when Bishop John Moore gave a speech before Queen Mary II, about "religious melancholy."

Two subcategories of thought disorder are content-thought disorder, and formal thought disorder. CTD has been defined as a thought disturbance characterized by multiple fragmented delusions. A formal thought disorder is a disruption of the form (or structure) of thought. Also known as disorganized thinking, FTD affects the form (rather than the content) of thought. FTD results in disorganized speech and is recognized as a key feature of schizophrenia and other psychotic disorders (including mood disorders, dementia, mania, and neurological diseases). Unlike hallucinations and delusions, it is an observable, objective sign of psychosis. FTD is a common core symptom of a psychotic disorder, and may be seen as a marker of severity and as an indicator of prognosis. It reflects a cluster of cognitive, linguistic, and affective disturbances that have generated research interest in the fields of cognitive neuroscience, neurolinguistics, and psychiatry.

Eugen Bleuler, who named schizophrenia, said that TD was its defining characteristic. Disturbances of thinking and speech, such as clanging or echolalia, may also be present in Tourette syndrome; other symptoms may be found in delirium. A clinical difference exists between these two groups. Patients with psychoses are less likely to show awareness or concern about disordered thinking, and those with other disorders are aware and concerned about not being able to think clearly.

Thought content is the subject of a person's thoughts, or the types of ideas expressed. Mental health professionals define normal thought content as the absence of significant abnormalities, distortions, or harmful thoughts. Normal thought content aligns with reality, is appropriate to the situation, and does not cause significant distress or impair functioning.

A person's cultural background must be considered when assessing thought content. Abnormalities in thought content differ across cultures. Specific types of abnormal thought content can be features of different psychiatric illnesses.

Examples of disordered thought content include:

Thought process is the form, flow, and coherence of thinking. This is how language is used and ideas put together. A normal thought process is logical, linear, meaningful, and goal-directed that demonstrates rational, sequential connections between thoughts that allows others to understand. Thought process is not what a person thinks, rather it is how a person expresses their thoughts.

Formal thought disorder (FTD), also known as disorganized speech or disorganized thinking, is a disorder of a person's thought process in which they are unable to express their thoughts in a logical and linear fashion. Mild forms of disorganised speech are quite common, and to be considered as a diagnostic criterion for psychosis it must be severe enough to prevent effective communication. Disorganized speech is a core symptom of psychosis, and therefore can be a feature of any condition that has a potential to cause psychosis, including schizophrenia, mania, major depressive disorder, delirium, postpartum psychosis, major neurocognitive disorder, and substance induced psychosis. FTD reflects a cluster of cognitive, linguistic, and affective disturbances, and has generated research interest from the fields of cognitive neuroscience, neurolinguistics, and psychiatry.