Human: Is it true that the human body has a natural antidepressant? Assistant: 
Yes, the human body has a natural antidepressant. The hormone melatonin is produced naturally by the pineal gland in the brain and is responsible for regulating sleep/wake cycles. Melatonin levels are highest during the night and lowest during the day. Low levels of melatonin have been linked to depression, so the human body has a natural antidepressant.