What are formal thought disorders?

Formal Thought Disorders

Formal thought disorders (FTD) are disturbances in the form or structure of thinking rather than the content, characterized by disruptions in the organization, flow, and connectivity of thoughts as manifested in a person's speech and communication patterns. 1

Types of Formal Thought Disorders

Positive Formal Thought Disorders

• Loose associations: Disconnected or poorly connected thoughts where ideas shift from one subject to another without logical connections 2
• Illogical thinking: Reaching conclusions that don't follow logically from premises 2
• Impaired discourse skills: Difficulty maintaining coherent conversation 2
• Derailment: Gradual or sudden deviation from the topic of conversation 3
• Perseveration: Persistent repetition of words, ideas, or topics 4
• Peculiar word use: Using words in unusual or idiosyncratic ways 5
• Peculiar sentence construction: Unusual syntax or grammar that impairs comprehension 5
• Peculiar logic: Drawing conclusions using faulty reasoning patterns 5

Negative Formal Thought Disorders

• Poverty of speech: Restriction in the amount of speech, with brief and empty responses 5
• Poverty of content of speech: Speech that conveys little information despite adequate quantity 4
• Weakening of goal: Inability to maintain the goal of communication throughout discourse 5

Clinical Significance

• FTD is present in most psychiatric disorders but has been traditionally linked to schizophrenia 1
• FTD is the only symptom under genetic influence in schizophrenia as shown in linkage studies 1
• In children with schizophrenia, three characteristic communication deficits are observed: loose associations, illogical thinking, and impaired discourse skills 2
• Rates of incoherence and poverty of speech content are low in children with schizophrenia 2
• FTD is a dimensional, phenomenologically defined construct that can be clinically subdivided into positive versus negative and objective versus subjective symptom clusters 1

Differential Diagnosis

• When assessing a child's thinking, it's important to differentiate the thought disorder of psychosis from developmental delays or language disorders 2
• Individuals with OCD and absent insight or delusional beliefs may be erroneously diagnosed as having a psychotic disorder if their lack of insight is not recognized as part of OCD 2
• Worries and ruminations characteristic of generalized anxiety disorder and depression are typically about real-life concerns and tend to be less irrational and ego-dystonic than in OCD 2
• Patients with schizophrenia with absent insight or delusional beliefs should be appropriately diagnosed and treated, rather than erroneously diagnosed as having a primary psychotic disorder 2

Neurobiological Basis

• Positive FTDs are related to synaptic rarefication in the glutamate system of the superior and middle lateral temporal cortices 1
• Cortical volume of the left superior temporal gyrus is decreased in patients with schizophrenia who have positive FTD in structural MRI studies 1
• Semantic network dysfunction in positive FTD has been demonstrated in experiments of indirect semantic hyperpriming 1

Assessment and Diagnosis

• FTD can be assessed using standardized measures such as the Thought and Language Index (TLI), which includes subscales for impoverishment of thought and disorganization of thought 5
• Poverty of speech, perseveration, and peculiar word use are significant factors differentiating first-episode psychosis patients from controls 5
• In acute schizophrenia, speech differs from that in mania by conveying little information and adhering to previously mentioned ideas and topics 4
• Cultural, developmental, and intellectual factors need to be taken into account in the diagnostic assessment of thought disorders 2

Treatment

• In acute positive FTD, antipsychotics are effective 1
• A subgroup of patients have treatment-resistant, chronic, positive or negative FTD 1
• Specific psychotherapy targeting FTD has not yet been well-developed 1

Historical Context

• Early descriptions of thought disorders date back to the 19th century with Esquirol 3
• Emil Kraepelin described akataphasia (inability to find the appropriate expression for a thought) in patients with dementia praecox 3
• Bleuler and Kretschmer identified a generalized "loosening of associations" in schizophrenic patients 3
• Carl Schneider described several Formal Thought Disorders such as derailment, fusion, omission, suspension, and driveling 3
• Nancy Andreasen reclassified FTDs and introduced a scale to assess them at the end of the 20th century 3