More than one million people in South Korea suffered from so-called "mood disorder" in 2020 according tothe country's national health insurance agency.
It says "mood disorder" is a mental state,when dramatic changes or extremes of mood continue for a long time,causing depression or bipolar disorder.
Data shows women and younger adults are more prone to it.
Since 2016, South Korea has seen an annual average increase of around 7 percent in the number of people seeking medical treatment for the disorder.
Experts cite mounting stress in people's daily lives.