The Diagnostic and Statistical Manual of Mental Disorders - or DSM - is a book full of lists of symptoms, strange sounding names, codes and guidelines. It's also a book that changes lives. Its champions say it is simply a system of classification, a diagnostic tool. Its critics claim it is more - it decides what is and isn't a disease and that every time a new version is published an increasing number of people are labelled mentally ill.
And for every diagnosis in the DSM, there is a corresponding medical treatment waiting in the wings.
In May 2013, the American Psychiatric Association will publish the latest edition of their DSM and it is likely to cause tension within the American psychiatric establishment.
But why is this medical-looking manual causing such controversy?
Where some say the previous DSM was responsible for pathologising childhood, critics of the new edition will medicalise grief.
Are the intense feelings most people experience after the death of a loved one misery or melancholia? That is the ongoing debate, the result of which will have an impact on millions of people and our understanding of a fundamental human reaction.
In a post-Prozac world, when normal becomes abnormal, medication generally follows. An estimated 8 to 10 million people lose a loved one every year and something like a third to a half of them suffer depressive symptoms for up to a month afterward. How much does the pharmaceutical industry stand to benefit if an extra 5 million people a year are prescribed anti-depressants?
Matthew Hill investigates the DSM, its decisions over what is and is not a mental illness, and the people behind it.
Producer: Gemma Newby
A Sparklab production for BBC Radio 4.