Thought Disorder (TD)
Thought disorder (TD), also known as a formal thought disorder (FTO), refers to patterns of disorganized thought and speech. Some of these are known as derailment, poverty of speech, tangentiality, illogicality, perseveration, neologism, clanging, echolalia and thought blocking. Researchers further divide these into disorders that involve speech "content" or "form." These disorders involve the inability to clearly express thoughts or to reply to others in ways that make sense. Thought disorders are symptomatic of schizophrenia, depression, mania, Tourette syndrome or delirium.