How are language deficits relevant to people with schizophrenia?
Language may be altered in people with schizophrenia and may present in the form of disorganised speech. Tasks designed to assess language ability include; letter fluency tasks that assess the ability to generate words starting with a particular letter; and category fluency tasks that assess the ability to name words within a specified category. Working memory is needed for both letter and category fluency as participants must organise and retrieve relevant information.
Other tests designed to assess language include: Boston Naming task; Wechsler Adult Intelligence Scale comprehension (WAIS), including the subtest information, similarities and vocabulary, WAIS verbal memory, verbal fluency, National Adult Reading Test / Wide Range Achievement Test, Controlled Oral Word Association Test, Category Instance Generation Test, Multiple Choice Vocabulary Test, Hopkins Verbal Learning test, California Verbal Learning Test, Rey Auditory Verbal Learning Test, semantic priming tasks and Lexical Decision Task and the Peabody Individual Achievement reading comprehension. Latent Semantic Analysis is a fairly new technique that estimates the degree of incoherence in language use.
What is the evidence for language ability in people with schizophrenia?
Compared to people without schizophrenia, moderate to high quality evidence shows large effects of more incoherent speech, impaired letter and category fluency, verbal learning, verbal working memory, and semantic priming in people with schizophrenia. People with schizophrenia with severe negative or disorganised symptoms were most impaired on verbal fluency. Moderate quality evidence also found impaired vocabulary and word fluency in people with first-episode, youth-onset, or late-onset schizophrenia.
Overall, moderate to high quality evidence found greater improvements in verbal fluency in people with schizophrenia taking second generation antipsychotics than in people with schizophrenia taking first generation antipsychotics. For specific second generation antipsychotics, quetiapine, olanzapine and clozapine improved overall language ability, but there were no improvements with risperidone. For first-generation haloperidol, there were improvements in verbal learning and delayed verbal recall, but not in verbal fluency.
Moderate to high quality evidence found improved performance on verbal learning tasks was associated with better social behaviour, social skills, and problem solving.
Compared to people with bipolar disorder, moderate to high quality evidence shows a small effect of poorer performance on word association and verbal learning tests in people with schizophrenia.
Green - Topic summary is available.
Orange - Topic summary is being compiled.
Red - Topic summary has no current systematic review available.