Depression is a mood disorder whereby feelings of sadness, unhappiness, gloom, hopelessness, despair, loss, misery, and discouragement last for a long time and interrupt daily activities. It is caused by the chemical changes in the brain and stressful life events. Certain medications served for various treatments alter brain chemicals that lead to depression. For example, Accutane, which is prescribed for the treatment of severe acne, can cause depression.