Emotional regulation refers to the psychological processes involved in the control of various aspects of emotion. This includes controlling the feeling, cognitive, physiological, and behavioral aspects of our emotional functioning.
It is thought that depression can affect a child's emotional regulation negatively by interfering with its normal processes.
For example, a depressed child may react more intensely to an innocent comment from a peer. She may become very irritated, angry, and lose her temper by yelling, or she may quickly become sad and frustrated and begin crying. Her reaction may make it more difficult to manage her emotions by using techniques such as self-soothing, distraction, or talking it out.
Of course, not all depressed children have issues with emotional regulation -- and emotional regulation tends to mature as a child does. However, if you notice that your child has difficulty controlling her emotions or behaviors, her reactions seem disproportionate to the situation, and she has additional symptoms of depression, it is important to speak with her pediatrician or other mental health provider for an evaluation.
Gabrielle I. Liverant, Timothy A. Brown, David H. Barlow, and Lizabeth Roemer. Emotional Regulation in Unipolar Depression: The Effects of Acceptance and Suppression of Subjective Emotional Experience on the Intensity and Duration of Sadness and Negative Affect. Behaviour Research and Therapy. 46(11).
Garcia-Andres, Esther, Huertas-Martinez, J. Antonio, Ardura, Aranzazu, Rernandez-Alcaraz, Camino. Emotional Regulation and Executive Function Profiles of Functioning Related to the Social Development of Children. Procedia: Social and Behavioral Sciences. 5(2010): 2077-2081.