Cognition in bipolar disorder and schizophrenia

What is cognition in bipolar disorder and schizophrenia?

Neurocognitive deficits are a core feature of both schizophrenia and bipolar disorder. People with either disorder may perform poorly on cognitive tasks assessing intelligence, memory, executive functioning, language, information processing and attention. Establishing differences in these cognitive domains may assist correct diagnosis and treatment of the two disorders.

What is the evidence for cognition in bipolar disorder compared to schizophrenia?

Moderate to high quality evidence found large effects of better overall cognition, attention, and social cognition, and medium-sized effects of better speed of processing, working memory, learning, reasoning, and problem solving in people with bipolar disorder. A small effect was found of better overall cognition in people with bipolar disorder compared to people with schizoaffective disorder (particularly depressive type), which remained across different cognitive domains, bipolar disorder type (I or I and II mixed), age, sex, duration of illness, antipsychotic use or no use, and symptom severity.

Moderate to high quality evidence found a medium-sized effect of higher premorbid IQ, and moderate to low quality evidence found a medium-sized effect of higher current IQ in people with first-episode bipolar disorder compared to people with first-episode schizophrenia. There were also medium-sized effects of better verbal memory and verbal fluency, and small effects of better working memory and processing speed in people with first-episode bipolar disorder.

Compared to controls without a mental illness, moderate to high quality evidence found a small effect of poorer pre-illness-onset cognitive functioning, and a medium-sized effect of poorer post-illness-onset cognitive functioning in people with bipolar disorder. In people with schizophrenia compared to controls, there was a medium-sized effect of poorer pre-illness-onset cognitive functioning and a large effect of poorer post-illness-onset cognitive functioning. Moderate quality evidence found similar, medium to large effects of poor semantic inhibition in people with bipolar disorder and in people with schizophrenia when compared to controls.

A medium-sized effect was found of better social cognition in people with bipolar disorder on Theory of Mind and negative facial emotion recognition tasks, particularly in male patients, but no differences between bipolar disorder and schizophrenia on positive (happy) facial emotion recognition tasks.

September 2021

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Last updated at: 4:01 am, 17th October 2021
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