Some symptoms of depression include, loss of sleep or over sleeping, finding previously enjoyed activities difficult, feeling hopeless, loss of control over negative thoughts, not eating or uncontrollable eating, irritability, thoughts that life is not worth living, etc. (Helpguide).
While depression does not seem serious, if a child is exposed to domestic violence and develops depression and does not get help, it could get progressively worse over time. As a child gets older the symptoms of depression can become more serious and even life threatening.
Another well documented outcome of witnessing or experiencing domestic violence is post traumatic stress disorder. While it is not as commonly seen as depression, post traumatic stress disorder can be just as, if not more, serious than depression and have more serious symptoms. Like