The Pacific Ocean is the largest ocean in the world at 155,557,000 sq km.   The Atlantic Ocean is the second largest ocean in the world at 76,762,000 sq km.
The cause of major depressive disorder is a combination of brain chemistry, family history, and psychosocial environment. It is not certain which of these factors dominates, but abnormal levels of the neurotransmitters norepinephrine, serotonin, and dopamine are closely linked with depression.
Major Depressive Disorder. The leading cause of disability in the U.S. for ages 15 to 44.3. Affects approximately 14.8 million American adults, or about 6.7 percent of the U.S. population age 18 and older in a given year.