Mood disorders such as depression can impact cognitive functioning. People with major depression (MD) can have difficulty thinking clearly, making decisions, and remembering things. Although these behaviors mimic those found in dementia, research focusing on the link between MD and dementia has yet to prove a definitive relationship. Reasons for this include use of diverse participant samples, a wide variety of diagnostic tools, and attention to a broad range of symptoms. Some studies have focused on people with dementia, while others have looked only at mild cognitive impairment (MCI). Similarly, some studies examine clinical diagnosis of MD in relation to dementia onset while others pay closer attention to depressive symptoms.
In an attempt to gather a more conclusive assessment of the link between MD and dementia, Melanie Luppa of the Institute of Social Medicine, Occupational Health, and Public Health at the University of Leipzig in Germany conducted a far reaching analysis on over 1,200 participants over the age of 75 over an eight year period. Baseline interviews gauged clinical MD symptoms, mood, and cognitive capacity. The participants were then re-evaluated every 18 months for the entire 8 years. This method allowed Luppa to determine which diagnostic tools and targets were most effective to clarifying a relationship between MD and dementia in older adults.
After reviewing the longitudinal data, Luppa found that MD did not directly predict dementia in those participants with normal cognitive functioning at baseline. However, those who presented with MCI and mood problems were at increased risk of dementia. The participants who expressed thoughts of death were among the most at risk. Luppa used varying diagnostic approaches for her analysis and believes that this technique explains some of the inconsistencies in her findings. For example, existing medical and psychological conditions including disability, isolation and bereavement, that could affect cognitive functioning and mood could contribute significantly to depressive symptoms and dementia, yet none was targeted specifically in this study. Luppa believes that the findings of her study do suggest that mood problems could be early symptoms of dementia rather than risk factors for it. She added, “Further in-depth investigation with larger samples would help to understand the nature of depression in the context of incident dementia, and the mechanism linking both.”
Luppa, M., Luck, T., Ritschel, F., Angermeyer, M.C., Villringer, A., et al. (2013). Depression and incident dementia. An 8-year population-based prospective study. PLoS ONE 8(3): e59246. doi:10.1371/journal.pone.0059246
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