Q1: Is depression a mental illness?
Yes, clinical depression is a serious but treatable mental illness. Moreover, it is one of the most common mental illnesses. It is estimated that the rate of major depression could be as high as 15% among Americans adults.
Q2:  Can lack of sleep cause depression?
No. Lack of sleep alone cannot cause depression. Although lack of sleep is considered one of the signs of depression, it is often connected with other causes, such as other medical illnesses or psychological issues. That being said, chronic sleeping disorder can play an important role in depression.
Common depression triggers are:

• History of depression in the family
• Grief over the loss of a loved one through death, divorce, or separation
• Interpersonal clashes
• Physical, sexual, or emotional abuse
• Major life events
• Serious illness
• Substance abuse
• Being isolated or excluded from family, friends, or other social groups

Q3: Can children have depression?
Yes. Children can also be diagnosed with clinical depression. Children’s depression is characterized by the same triggers as in adult depression. Those factors include: changes in physical health, life events, heredity, environment, and chemical disturbance in the brain. Depressed children may experience disruptive changes in their behavior and normal lifestyle, often interfering with their friendships, schoolwork, special interests, and family life.