F[subscript 0]-based acoustic measures were extracted from a brief, sentence-final target word spoken during structured play interactions between mothers and their 3- to 14-month-old infants and were analyzed based on demographic variables and DSM-IV Axis-I clinical diagnoses and their common modifiers. F[subscript 0] range (?F[subscript 0]) was negatively correlated with infant age and number of children. ?F[subscript 0] was significantly smaller in clinically depressed mothers and mothers diagnosed with depression in partial remission, relative to nondepressed mothers, mothers diagnosed with depression in full remission, and those diagnosed with depressive disorder not otherwise specified. ?F[subscript 0] was significantly lower in mothers experiencing their first major depressive episode relative to mothers with recurrent depression. Deficits in ?F[subscript 0] were specific to diagnosed clinical depression, and were not well predicted by elevated self-report scores only or by diagnosed anxiety disorders. Mothers with higher ?F[subscript 0] had infants with reportedly larger productive vocabularies, but depression was unrelated to vocabulary development. Implications for cognitive-linguistic development are discussed.