Depression is a common mental disorder, characterized by sadness, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, feelings of tiredness, and poor concentration. The most spread form of depression is Major Depressive Episode (MDE). MDE can be long-lasting or recurrent, substantially impairing an individual’s ability to function at work or school or cope with daily life. When mild, people can be treated without medicines but when depression is moderate or severe they may need medication and professional talking treatments. MDE is a disorder that can be reliably diagnosed and treated by non-specialists as part of primary health care. Specialist care is needed for a small proportion of individuals with complicated depression or those who do not respond to first-line treatments. - World Health Organization
The data on Major Depressive Episode are taken from National Survey on Drug Use and Health.