Overgeneral autobiographical memory – an alteration in the specificity of memory from an individual’s life – is a characteristic of bipolar I disorder and relates to executive function, according to a report published in Comprehensive Psychiatry.
"We found a greater prevalence of overgeneralized [autobiographical memory] in [bipolar disorder] patients compared to healthy controls," wrote lead study author Woo Jung Kim of Yonsei University in Seoul, South Korea, and his associates. "Our results suggest [autobiographical memory] may be a characteristic of [bipolar disorder] along with certain cognitive functions."
The investigators recruited 28 bipolar I disorder patients from inpatient and outpatient clinics at Severance Mental Health Hospital, and 28 healthy age- and sex-matched controls. The patients were between the ages of 20 and 50.The researchers gave all participants the autobiographical memory test (AMT), a word-cuing technique aimed at assessing the degree of specificity of autobiographical memory, and a 2-hour neuropsychological battery to assess general intelligence, attention, verbal memory, verbal fluency, visual memory, and executive functions.
The AMT was adapted to Korean culture, using five positive adjectives (happy, successful, safe, interested, and loved) and five negative adjectives (hurtful, angry, lonely, failed, and dangerous). The words were written on paper cards and shown to participants one at a time, while those administering the test encouraged participants to recall specific memories and describe them in as much detail as possible within 1 minute each.
Each patient was interviewed using the Mini-International Neuropsychiatric Interview. Their residual mania symptoms were assessed using the Young Mania Rating Scale, and their depressive symptoms were assessed by the Montgomery-Asberg Depression Rating Scale. Patients with other medical or psychiatric comorbidities were excluded, as were those with mental retardation or a history of head trauma (Compr. Psychiatry 2014;55:290-7).
The investigators found the total and negative AMT scores to be significantly lower in the patients with bipolar disorder than in healthy controls. For example, among the patients with bipolar disorder, the total autobiographical memory test scores were 3.86 plus or minus 2.85, compared with 5.32 plus or minus 2.57 among the healthy controls. Meanwhile, the negative autobiographical memory test scores were 1.86 plus or minus 1.38 among the patients with bipolar disorder and 2.75 plus or minus 1.40 among the healthy controls.
In addition, the patients with bipolar disorder "tended to report more general and fewer specific positive memories than did the healthy controls, although the difference was not statistically significant." The bipolar disorder group had significantly lower verbal memory, verbal fluency, and visual memory test scores than the healthy controls, but the results of tests for executive function were not different between the groups.
In bipolar disorder patients, the AMT scores correlated significantly with intelligence and perseverative errors. In healthy controls, they correlated with verbal memory and fluency.
The investigators cited several limitations. The sample size was fairly small, but it was similar to that of previous studies of autobiographical memory and bipolar disorder, they said. None of the patients in the study had psychotic symptoms at the time of enrollment, but the investigators did not access the patients’ prior history of such symptoms.
"Future research should investigate the specific [autobiographical memory] neural network in [bipolar disorder] individuals and examine the relationship between [autobiographical memory] and psychosocial functions and quality of life," the authors wrote. This may provide insight into the benefit of additional treatment focusing on overgeneral autobiographical memory in bipolar disorder, they said.
This study was supported by the Korea Healthcare Technology R&D Project of the Ministry of Health & Welfare of the Republic of Korea. The authors reported no relevant financial disclosures.