The Challenge of Antidepressant Therapeutics in Alzheimer's Disease

The link between depression and Alzheimer's disease (AD) is controversial, because it is not clear if depression is an independent risk factor for the disease or a prodromal symptom in the older population. Cerebral amyloid-β (Aβ) peptide deposition is associated with both cognitive symptoms and neuropsychiatric symptoms (NPS), which may be a biological mechanism of compensation. Despite the widespread use of antidepressant therapeutics (30-50% of patients with AD/dementia are on antidepressants), there is mixed evidence regarding the benefits from their use in AD depression. Monoaminergic antidepressant drugs have shown only modest or no clinical benefits. Therefore, it is important to understand the reason of this drug-resistance and the relationship between antidepressant drugs and the Aβ peptide. The goal of the present review is to highlight the etiology of depression in patients affected by AD in comparison to depressive disorders without AD, and to speculate on more appropriate and alternative therapeutics.