Final answer:
Depression is a common mental disorder characterized by severe depressive moods lasting longer than two weeks. Treatments include psychotherapy and medication.
Step-by-step explanation:
Depression is a common mental disorder characterized by severe depressive moods lasting longer than two weeks. The exact causes of depression are unknown, but it is believed to involve both genetic and environmental factors. Treatments for depression include psychotherapy, electroconvulsive therapy, deep-brain stimulation, and prescription medications. Research suggests that depression may be caused by a decrease in neurotransmitters like norepinephrine and serotonin, although the exact mechanisms are not fully understood.