More than 4 percent of the world's population lives with depression, and women, youth and the elderly are the most prone to its disabling effects, the World Health Organisation (WHO) says.
An estimated 322 million people suffered depressive disorders in 2015, a rise of 18.4 percent in a decade, as people live longer, the United Nations agency said on Thursday.
Global economic losses exceed US$1 trillion (NZ$1.38 trillion) a year, it said, referring to lost productivity due to apathy or lack of energy that lead to an inability to function at work or cope with daily life.
Depression is 1.5 times more common among women than men, it said.
A further 250 million people suffer anxiety disorders, including phobias, panic attacks, obsessive-compulsive behaviour and post-traumatic stress disorder, the report said.
Some 80 percent of those stricken with mental illness live in low- and middle-income countries, removing the stereotype that mental health is a problem for rich nations alone.
Three age groups are particularly vulnerable to depression - youth, pregnant or post-partum women, and the elderly.
Around 15 percent of women will suffer not just 'the blues', but a diagnosable case of depression.
An estimated 800,000 people die from suicide each year, a "pretty horrifying figure", Dr Dan Chisholm of WHO's Department of Mental Health and Substance Abuse said.
"It is more common in males in higher-income countries but more common in females in lower- and middle-income countries".
The WHO is running a campaign to tackle stigma and misconceptions called Depression: Let's Talk.
"We feel that is a key first step, that if we want to bring mental health, depression and other mental disorders out of the shadows, we need to be able to talk about it," Chisholm said.
If you or someone you know is in crisis and needs immediate help, call Lifeline on 0800 543 354 or the Suicide Prevention Helpline on 0508 828 865.