Depression is a condition in which a person experiences persistent feelings of sadness and loss of interest. In addition to emotional and behavioral changes, depression can have physical symptoms as well. Depression may affect a person’s ability to perform normal, day-to-day activities. Symptoms in adolescents and teens may include anxiety, anger and avoidance of social interaction. There are many probable causes of depression, including biological factors, neurotransmitters, hormones, genetics, life events and early childhood trauma. Treating depression will vary depending on the severity of the condition, but may include medication, psychotherapy, electroconvulsive therapy (ECT) and hospitalization.