Past Issues

Depression and dementia coexist often. To elucidate their relationship that the onset of depression precedes dementia is clinically worthwhile. Both conditions may share common etiologies. Depression may etiologically contribute to the de-velopment of dementia, or it may be just a prodrome of dementia. Evidences have suggested the possible shared common etiologies of depression and dementia are ischemic brain lesions, abnormal states in nutrition, and the existence of apolipo-protein E gene (ApoE). Ischemic brain disease may play a surrogate rôle to de-velop both depression and cognitive impairment. Nutrition status, such as polyun-saturated fatty acids or homocysteine, is the major interest of this issue. Subjects carrying the ApoE ε4 allele of the have a higher risk of developing Alzheimer’s disease (AD), but its association with depression is inconsistent. Depression can activate adrenal cortical gonadotropin secretion, which thus can have neurotoxic effect on the hippocampus. One meta-analysis study has been found that there was an association exists between interval between diagnoses of depression and AD and an increased risk of developing AD, supporting that depression may cause AD. However, clinical studies do not optimistically suggest cognitive prognosis of late life depression after a course of antidepressant treatment. The last possibility is that a neurodegenerative process underpins when depression emerges before the threshold of diagnosis of dementia can be made. Cognitive dysfunction in late-life depression may be explained by the depression itself representing a prodromal phase of dementia. That a recent history of depression is associated with increased risk of Alzheimer’s disease, can support the speculation. Current evidence sup-ports all possibilities that depression can be one of the causes, a prodromal sign of dementia, or share common etiologies with dementia. Further treatment focusing on the relationships is needed to prevent the elderly patients with depression from converting to dementia later on.