The claim that “one in four” of us will suffer from a mental health problem is popular amongst campaigners, politicians and the media. But this leads you to a simple question – where is this figure from and what’s the evidence? This was exactly what neuroscientist Jamie Horder asked, and far from being simple, it led him on quite a journey. So do we really know how many people are likely to develop mental health problems – Elizabeth Cassin and Charlotte McDonald find out. Presenter: Charlotte McDonald Producer: Elizabeth Cassin