Cognition means thought, and the serious mental illness known as schizophrenia typically leads to a person's thoughts becoming disorganized. What are called formal thought disorders tend to occur, which can make it difficult for the person to communicate with others because they lead to confused speech. Communication is made even more difficult because in schizophrenia the ability to pick up social cues from others is decreased. Other effects of schizophrenia on cognition can cause problems with memory, concentration and the ability to organize oneself.
Symptoms of schizophrenia can be mild or severe, and are divided into two sorts: positive and negative. The effect of schizophrenia on cognition leads to thought disorders, and these are classed as positive symptoms of schizophrenia, as they are features which are not normally present in people without the illness. Other positive symptoms include delusions, where bizarre ideas are held to be true, and hallucinations, where things appear real which are not actually there. Negative symptoms of schizophrenia are things which are lacking in the person with schizophrenia which would normally be present in someone without the illness, and these include flattened emotions, self-neglect and withdrawal from society.
The effect of schizophrenia on cognition causes thought disorders which can make a person's speech swap from one topic to another seemingly at random. This is described as having loose associations, because one topic hardly seems linked to the next. Another odd symptom is that the flow of speech seems to suddenly stop heading in a certain direction, like a train coming off the rails, and this is known as derailment. People affected by these thought disorders generally believe they are making sense, although, to the listener, one irrelevant word from a sentence may seem to launch the next topic of conversation.
Sometimes people with schizophrenia experience a thought disorder where they continually repeat certain words or phrases. This is known as perseverance. The effect of schizophrenia on cognition can also result in a tendency to invent completely new words, known as neologisms. These disorders may cause speech to appear quite odd, as may another thought disorder known as clang, where people use a lot of rhymes when they are speaking. What is called thought block can also occur, causing long pauses in speech, and abstract thinking, which is used to understand the meaning of a proverb, for example, may be impossible.
Although the effect of schizophrenia on cognition might seem extreme, similar thought disorders occur occasionally in people who do not have the disease. For example, when people become excessively tired their speech can become disorganized. The thought disorders associated with schizophrenia are typically more severe, and generally improve when the disease is treated. A number of schizophrenia subtypes exist, such as paranoid schizophrenia, but all are typically managed with a combination of antipsychotic drugs, together with psychological and social forms of schizophrenia support.