LOS ANGELES – Anhedonia is typically thought of as part of depression, but findings from a study of patients with Alzheimer’s disease suggest that this common but poorly understood aspect of AD is a dissociable construct.
If confirmed in larger trials, the findings suggest that parsing anhedonia as a separate construct could allow for the condition to be treated separately, potentially enriching affected patients’ quality of life, Laura E. Natta reported in a poster at the annual meeting of the American Association for Geriatric Psychiatry.
"Mood symptoms can adversely affect executive functioning, especially working memory, which has ramifications for successful management of day-to-day activities," she explained.
Of 87 patients with mild to moderate AD who were included in the study, 8 had both depression and anhedonia, 12 had only anhedonia, 25 had only depression, and 34 had neither condition. Eight participants were excluded due to their inability to complete the full neuropsychological battery. Those with both depression and anhedonia had significantly poorer working memory as measured with the Wechsler Adult Intelligence Scale-III Digit Span Backwards test (WAIS-III DSB) than did those with only depression and those with neither condition (mean scores of 2.4, 5.1, and 4.1 digits, respectively). Those with only anhedonia had significantly poorer working memory than did those with only depression (mean scores of 3.7 and 5.1 digits, respectively), said Ms. Natta of the Brain Behavior and Aging Research Center of the Veterans Affairs Greater Los Angeles Healthcare System, West Los Angeles.
"Although not significant, on DSB the group with anhedonia performed better than the group with both depression and anhedonia. There was no significant difference between the anhedonia group and the group with neither depression nor anhedonia on the DSB," she said.
The findings demonstrate that the effect of combined depression and anhedonia on working memory is greater than the effect of anhedonia alone, and that anhedonia, via its effect on working memory, may contribute to difficulties with activities of daily living among patients with AD.
Though limited by a small sample size, a limited measure of anhedonia, and a lack of adjustment for other cognitive symptoms, the findings supplement those from other recent studies demonstrating that nondemented depressed patients with anhedonia have a cognitive profile that differs substantially from nondemented depressed patients without anhedonia, suggesting this is also the case in patients with AD, Ms. Natta noted.
The study comprised 17 women and 70 men, mean age 79 years. All underwent clinical assessment via the Mini Mental State Exam, the Mattis Dementia Rating Scale, and the WAIS-III Digit Span Forwards and Digit Span Backwards. Global symptoms of depression were assessed with the Hamilton Depression Scale or the Cornell Scale for Depression in Dementia. Anhedonia was assessed with the global specific rating on the Social-Emotional Withdrawal Scale on the Assessment of Negative Symptoms in AD.
Further clarification of the nature and influence of anhedonia in patients with and without depression is needed, given the potentially important diagnostic and treatment implications of the findings, not only for patients with AD, but for those with various other psychiatric and neurological disorders as well, she concluded.
Support for this study was provided by the National Institute of Mental Health. Support was also provided by Merit Review and CDA to individual authors.