Depression Affects Kids as Young as 3 - Web MD Childhood is typically viewed as a carefree, happy time, but depression can occur even in preschoolers as young as age 3, according to a recent update. For years, experts thought that young children would be too developmentally immature to experience depression, says Joan L. Luby, MD, a professor of psychiatry at Washington University in St. Louis School of Medicine, who has researched the topic for 20 years. She wrote an update for the journal Current Directions in Psychological Science. Parents may wonder what the typical 3-year-old has to be depressed about, but Luby says it is not necessarily because something bad or stressful is occurring. "It's a brain disorder that, basically what our findings are showing, can arise as early as age 3 and not necessarily due to bad things happening in life."