John Moore, who was a bishop, had a speech in front of Queen Mary II, about "religious melancholy.

[12] 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.

[14] Disturbances of thinking and speech, such as clanging or echolalia, may also be present in Tourette syndrome;[15] other symptoms may be found in delirium.

[19] Normal thought content aligns with reality, is appropriate to the situation, and does not cause significant distress or impair functioning.

[12][13] The two groups were posited to be at either end of a spectrum of normal speech, but later studies showed them to be poorly correlated.

FTD may include incoherence, peculiar words, disconnected ideas, or a lack of unprompted content expected from normal speech.

A number of studies indicate that FTD in mania is marked by irrelevant intrusions and pronounced combinatory thinking, usually with a playfulness and flippancy absent from patients with schizophrenia.

[36][37][38] The FTD present in patients with schizophrenia was characterized by disorganization, neologism, and fluid thinking, and confusion with word-finding difficulty.

The study also found an association between pre-index assessments[clarification needed] of social, work and educational functioning and the longitudinal course of FTD.

[41] Semantic network impairment in people with schizophrenia—measured by the difference between fluency (e.g. the number of animals' names produced in 60 seconds) and phonological fluency (e.g. the number of words beginning with "F" produced in 60 seconds)—predicts the severity of formal thought disorder, suggesting that verbal information (through semantic priming) is unavailable.

[35] Future research is needed to clarify whether there is an association with FTD in schizophrenia and neural abnormalities in the language network.

Studies have found that glutamate dysfunction, due to a rarefaction of glutamatergic synapses in the superior temporal gyrus in patients with schizophrenia, is a major cause of positive FTD.

[35] FTD is not solely genetically determined, however; environmental influences, such as allusive thinking in parents during childhood, and environmental risk factors for schizophrenia (including childhood abuse, migration, social isolation, and cannabis use) also contribute to the pathophysiology of FTD.

[35] Large randomised controlled trials evaluating the effectiveness of CBT for treating psychosis often exclude individuals with severe FTD because it reduces the therapeutic alliance required by the therapy.

[50] Kircher and colleagues have suggested that the following methods should be used in CBT for patients with FTD:[35] Language abnormalities exist in the general population, and do not necessarily indicate a condition.

[1][52] To distinguish thought disorder, patterns of speech, severity of symptoms, their frequency, and any resulting functional impairment can be considered.

[53] FTD is a hallmark feature of schizophrenia, but is also associated with other conditions that can cause psychosis (including mood disorders, dementia, mania, and neurological diseases).

An older use of the term "thought disorder" included the phenomena of delusions and sometimes hallucinations, but this is confusing and ignores the clear differences in the relationships between symptoms that have become apparent over the past 30 years.

The text said that some clinicians use the term "formal thought disorder" broadly, referring to abnormalities in thought form with psychotic cognitive signs or symptoms,[95] and studies of cognition and subsyndromes in schizophrenia may refer to FTD as conceptual disorganization or disorganization factor.

For the sake of clarity, the unqualified use of the phrase "thought disorder" should be discarded from psychiatric communication.

[98] Derailment, loss of goal, poverty of content of speech, tangentiality and illogicality are particularly characteristic of schizophrenia.

[98] More prominent negative symptoms generally suggest a worse outcome; however, some people may do well, respond to medication, and have normal brain function.

[102] Treatment for thought disorder may include psychotherapy, such as cognitive behavior therapy (CBT), and psychotropic medications.

[4][6] Psychotic disorders due to medical conditions and substance use typically consist of delusions and hallucinations.

[105] Psychoses such as schizophrenia and bipolar mania are distinguishable from malingering, when an individual fakes illness for other gains, by clinical presentations; malingerers feign thought content with no irregularities in form such as derailment or looseness of association.

[106] Negative symptoms, including alogia, may be absent, and chronic thought disorder is typically distressing.

[110] Hermann Rorschach developed this test to diagnose schizophrenia after realizing that people with schizophrenia gave drastically different interpretations of Klecksographie inkblots from others whose thought processes were considered normal,[111] and it has become one of the most widely used assessment tools for diagnosing TDs.

Although TD is typically associated with psychosis, similar phenomena can appear in different disorders and leading to misdiagnosis.