People who experience prolonged depressive symptoms starting in young adulthood may have worse thinking and memory skills in middle age, a new study has found. The startling finding busts the myth that dementia is an old person’s problem: the seeds of brain decline can be sown decades in advance. “The processes that lead to dementia begin long before signs of the disease become apparent, and previous research has shown that black adults have a higher risk of dementia than white adults,” said study author Leslie Grasset, PhD, of University of Bordeaux in France. “Our study found that prolonged …