Heterogeneity of elderly depression: Increased risk of Alzheimer's disease and Aβ protein metabolism

► Depression may increase the risk for AD, even in patients with early-onset depression. ► Serum Aβ40/Aβ42 ratio was higher in both early- and late-onset MDD than in controls. ► Serum Aβ40/Aβ42 ratio was negatively correlated with the age at MDD onset.