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This is the BBC World Service. I'm Charlotte

McDonald. The claim that one in four of us will suffer from a mental health problem is popular amongst campaigners, politicians, international organizations and the media.

One in four people in the world will be affected.

One in four people will experience at least one

diagnosable mental health problem.

But when you try to track down where the figure came from, it's

more difficult than you might think. Jamie Hoorder is a neuroscientist at Kings College

London in the UK. My interest really was sparked back in 2009 and there was a big mental health campaign at that time

which is still going on I believe called Time to Change and this was a campaign

about trying to reduce the stigma of mental illness and one of the things that they quoted was

One in four of us will experience a mental health problem at some point in our lives.

And I'd seen that stat quoted elsewhere as well,

but I noticed that the details were changing each time I saw it.

So, for instance, sometimes it's quoted as being one in four people at any one time and other times it's over the whole of their lifespan and those are two quite different things.

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