The nature of depression in dementia: A narrative review

This article discusses psychological and clinical studies of depression as comorbid to different dementias and mild cognitive impairment (MCI). First, we summarize studies on the diagnosis and prevalence of depression in dementia patients; we will show that there are different ways of diagnosing depression in dementia, leading to some conflicting findings. Second, we discuss how depression can be a risk factor for the development of MCI and dementias, possibly due to depression impacting hippocampal function. Then, we discuss the nature and subtypes of depression in dementia as well as the relationship between the type (Alzheimer’s disease vs vascular dementia) and severity of dementia (e.g., mild vs advanced stage) and depression. Throughout the article, we will summarize relevant clinical and neural studies on depression in dementia, including the importance of diagnosing and treating depression in dementia patients. Our review shows the relationship between depression and dementia is bidirectional, there are different subtypes of depression, patients’ insight of their disease can exacerbate depression symptoms, and the severity of depression varies across dementia types. Importantly, this article provides a timely update on a prior review on the links between depression and dementia.