Mood disorders, including depression, are the most common mental disorders. One in four Canadians are diagnosed with depression at some point in their lives. Globally, depression is the leading cause of disability. Factors that may contribute to the occurrence of a mood disorder include traumatic events during early development and life stressors; genetic predisposition; and biochemical changes. It is a myth that mood disorders may be related to a lack of willpower or other character flaws.