Thought blocking, a phenomenon that occurs in people with psychiatric illnesses (usually schizophrenia), occurs when a person's speech is suddenly interrupted by silences that may last a few seconds to a minute or longer. When the person begins speaking again, after the block, they will often speak about a subject unrelated to what was being discussed when blocking occurred. It is described as being experienced as an unanticipated, quick and total emptying of the mind. People with schizophrenia commonly experience thought blocking and may comprehend the experience in peculiar ways. For example a person with schizophrenia might remark that another person has removed their thoughts from their brain.
When doctors diagnose thought blocking, it is important that they consider other causes of pauses in speech and expression, such as petit mal seizures, aphasia, hesitation brought on by anxiety, or slow thought processes. When looking for schizophrenia they may look for thought blocking. It is a common issue with schizophrenia patients.