Over time researchers have observed that depression follows a U pattern. First depression symptoms are high in young adulthood. Like the dip of a U, depression symptoms decrease in midlife, and the rounding back up of the U signifies the return of greater depressive symptoms in later years.
The results of some long-term longitudinal studies that investigated the peak in depression later in life showed that depression symptoms in older people are not caused solely by closeness to death or a decrease in physical health.
The increase in depressive symptoms is not marginally large, and may also possibly be linked to a decrease in quality of life that came with age. Further research is being conducted in order to gain a greater understanding of what is responsible for this later life depression.