New studies support the theory that depression and dementia are linked. Developmental psychologist Adam Davey of Temple's Department of Public Health says no matter what the nature of the relationship, the finding is an added impetus to treat depression. "To this point, depression is the only treatable piece of the equation, and so identifying and treating depression would be an important piece of the puzzle," Davey said. Doctors treating people with dementia say they hope to see more research on the exact relationship between depression and later decline of brain function.