No blood or imaging test can detect depression. Instead, a mental health professional, for example, a psychiatrist, therapist, or social worker, will ask about the child’s symptoms and behavior.
Looking at the child’s symptoms, the doctor will determine whether they have depression, another mental health condition, or both.
Caregivers can help a doctor make a diagnosis by keeping a list of symptoms. They should be prepared to answer questions about the child’s history, when symptoms first appeared, and whether there is a family history of depression.
The provider may want to meet with the child alone because some children, especially teens, may not feel comfortable discussing all of their symptoms in front of others.
Source Article from https://www.medicalnewstoday.com/articles/327292.php