Depressive disorder (also known as depression) is a common mental disorder.
Common symptoms are low mood or loss of pleasure or interest in activities for long periods of time (minimum 2 weeks).
Depression can affect all aspects of life, including relationships with family, friends and community. It is different from normal ups and downs of life as it causes impairment in functioning and can be highly distressing to the person suffering from it.
Depression can happen to anyone, however, those who are survivors of abuse, have experiences losses or experiencing stressful events are more likely to develop it.
More Info:
https://www.who.int/news-room/fact-sheets/detail/depression
https://www.yourhealthinmind.org/mental-illnesses-disorders/depression
https://www.beyondblue.org.au/mental-health/depression
https://www.healthdirect.gov.au/depression