The finding that depression can arise in childhood refuted theoretical literature suggesting that children would be developmentally too immature to experience depressive affects. Subsequently, developmental studies of the infant offspring of depressed mothers demonstrated that alterations in emotional expression were already occurring in infants at high risk for later depression. Building on these findings, empirical studies have shown that preschool-aged children can also manifest depression. Depressed preschoolers display age-adjusted manifestations of the same symptoms known to arise in older depressed children and adults. Clinical observations have supported the existence of depressive affects in infants and toddlers. Very early identification of depression may be important to the treatment of this known chronic and relapsing disorder.