Memory

What is memory and how is it measured?

Memory involves encoding, storage and retrieval of information. Short-term memory is the ability to remember information after several seconds or minutes; and long-term memory is the ability to remember information over a longer duration. Working memory involves information being temporarily held as well as manipulated. Semantic memory is memory for general facts, episodic memory is memory for personal events, prospective memory is memory for future actions, and retrospective memory is memory for past events. Most memory tasks assess retrospective memory by measuring recall and recognition.

What is the evidence regarding memory in people with bipolar disorder?

Compared to people without bipolar disorder (controls), high quality evidence shows a medium-sized effect of poor working memory, and moderate to high quality evidence shows a medium-sized effect of poor prospective and digit span memory in people with bipolar disorder. The effect for digit span backward was larger than the effect for digit span forward. Moderate to high quality evidence also shows small to medium-sized effects of poor verbal, visual, and working memory in people with first-episode bipolar disorder and in youth with bipolar disorder aged around 13 years. In older people with bipolar disorder (> 60 years), moderate quality evidence shows a medium-sized effect of poorer memory than in controls matched for age and years of education. Poor delayed recall in older patients was significant only during depression phases, while poor digit span in older patients was significant only during manic phases.

Moderate to high quality evidence suggests no differences in verbal, visual or working memory between first-degree relatives of people with bipolar disorder and controls, however high quality evidence found small effects of poorer verbal and visual memory in young first-degree relatives (aged 10 to 25 years).

Compared to people with first-episode schizophrenia, moderate to high quality evidence shows a medium-sized effect of better verbal memory in people with first-episode bipolar disorder, and moderate quality evidence shows a small to medium-sized effect of better working memory, with no differences in visual memory. Similarly, compared to first-degree relatives of people with schizophrenia, moderate to high quality evidence shows first-degree relatives of people with bipolar disorder have small to medium-sized effects of better verbal and working memory, with no differences in visual memory.

Compared to people with bipolar disorder and no history of psychotic symptoms, high quality evidence shows small effects of poorer verbal and working memory in people with bipolar disorder with a history of psychotic symptoms, with no differences in visual memory. There was also a small effect of poorer verbal memory in people with bipolar I disorder compared to people with bipolar II disorder, and no differences in working or visual memory.

Compared to people with major depression, moderate quality evidence shows a medium-sized effect of poorer verbal memory in people with bipolar disorder during euthymia, with no differences during depression.
High quality evidence suggests a small association between poorer memory and poorer general functioning, and moderate quality evidence suggests no changes in memory over time (~4-5 years) in people with bipolar disorder.

March 2019

Last updated at: 5:08 am, 31st March 2019
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