Selective deficit of autobiographical incident memory in subjects with bipolar disorder

Previous studies have suggested that episodic memory impairment is one of the trait-like markers of bipolar disorder (BD), and is also associated with the course of the illness. Autobiographical memory (AM) is a special type of episodic memory, and disruption of AM causes severe psychosocial dysfunctions in patients with various neuropsychiatric disorders. However, little is known about possible deficits in AM in BD. This study investigated AM performance of BD patients and the effect of aging on their memory function.

We assessed AM of particular incidents (incident AM) and AM of personal facts (semantic AM), focusing on 4 time periods in 31 BD patients and 38 normal controls. Each group was divided into younger and older subgroups. General episodic memory functioning was also assessed by a word list learning task.

While there were no impairments in semantic AM throughout the lifetime in either group, both the younger and older BD groups exhibited impairments in incident AM compared to controls, and this effect was more profound in the recent period in the older BD group. Performance on the word list learning test was not impaired in either subgroup of BD patients, indicating that general episodic memory function was preserved.

We are the first group to report relatively selective AM impairments in BD, which have severer effects upon recent incident memory, and seemed to worsen with aging and/or clinical course.