Depression is seen as low mood most of the day; irritable mood for the youth, Markedly diminished interest, marked loss of interest in almost all activities; observation of significant apathy. Significant weight loss or gain; Change in appetite, and consider failure to make expected make expected weight gain. First scientific research to demonstrate childhood depression was by Spitz and Wolf in 1965, who observed that infant between 6 and 11 months when separated from their primary caregiver, developed symptoms over weeks resembling adult depression.

Depression in children sometimes is masked by other behaviors like

conduct problems (hyperactivity, delinquency, aggressiveness, irritability),
somatic complaints (headache, stomach ache, and enuresis),
school problems (school phobia, poor school performance),
In some situations depressed children are less likely to make serious suicidal attempts, and more likely to show depressed appearance, anxiety (i.e., separation anxiety), irritability, frustration, tantrums, apathy and disinterest, lack of co-operation, withdrawal from family and friends, physical complaints (headache, stomach ache) etc. They are also likely to show impairment in interpersonal relationships, increased substance abuse, overreaction to criticism, unable to meet expectations, indecision, self-destructive behavior, problems with authority figures, and increased teenage pregnancy.

People who can assess:
Clinical Psychologist for individual psychotherapy, family therapy or group therapy
Psychiatrist for medications
When children don’t get helped:
When we feel a child is being moody
We start believing that the child is weak in handling life affairs
Counselors or other healthcare providers sometimes might not be trained to pick the clinical signs and symptoms.
Red Flags to be cautious of:
If a child is showing sudden change in mood, hopelessness with a higher intensity for a longer duration than his/her usual self.
Increased substance abuse
Express death wishes or life being a burden