The Diagnostic and Statistical Manual, whose updated fifth edition will include a range of new diagnoses, is a mythology, not a scientific text. It is created by American psychiatrists who meet in groups to consider whether or not a certain diagnosis should be included in the DSM. These groups meet a number of times so that they can say that their agreement about a certain diagnosis is reliable. Thus they could reliably agree that there is a mental disorder called Guardian Readers' Personality Disorder with the symptoms of a need to read this paper regularly, an overvaluation of the Guardian, and so on. Who knows, it might already be in the most recent version of the DSM.

In their book, Making Us Crazy: DSM – The Psychiatric Bible and the Creation of Mental Disorders – which won the Mind Book of the Year Award in 1999 – Herb Kutchins and Stuart A Kirk wrote: "DSM is a book of tentatively assembled agreements. Agreements don't always make sense, nor do they always reflect reality. You can have agreements among experts without validity. Even if you could find four people who agreed that the earth is flat, that the moon is made of green cheese, that smoking cigarettes poses no health risks, or that politicians are never corrupt, such agreements do not establish truth."

For any statement to be valid there has to be evidence for that statement outside of the statement itself. Thus any textbook of physical disorders will list not just the symptoms of each illness but evidence that exists separate from those symptoms and that is derived from a wide variety of tests. Apart from the disorders listed in the DSM as the result of brain trauma, there are no physical tests for any of the disorders listed in the DSM. No physical cause has been found for any of these mental disorders. The diagnosis you receive from a psychiatrist is no more than the psychiatrist's opinion of what you have told him. Go to another psychiatrist and you're likely to get a different diagnosis.

Why do psychiatrists accept such an unscientific document as the DSM? In her book, The Users and Abusers of Psychiatry, my colleague Lucy Johnstone wrote, "To admit the central role of value judgments and cultural norms [in the creation of the DSM] is to give the whole game away. The DSM has to be seen as reliable and valid, or the whole enterprise of medial psychiatry collapses."

Legal cases and medical insurance require any doctor or psychologist filling in the necessary forms to state a diagnosis. In the UK many psychiatrists, GPs and psychologists now see applying a DSM diagnosis to a patient as a pointless exercise, but feel that it is not in their patient's interest to refuse to fill in this part of the form. However, there are still far too many doctors and psychologists who are too intellectually lazy to think about patients as individuals, or too fond of the many freebies that the drug companies provide for them. These are the ones who spring to the defence of the DSM.

The people who come to the attention of psychiatrists and psychologists are feeling intense, often severe mental distress. Each of us has our own way of expressing anxiety and distress, but when under intense mental distress our typical ways become exaggerated. We become self-absorbed and behave in ways that the people around us find disturbing. Believing that when we're anxious it's best to keep busy can mean that our intense mental distress drives us into manic activity. A tendency to blame yourself and feel guilty can transmute into depression. A desire to keep things under control can become obsessions and compulsions. We need someone to help us to make sense of the terror that can come over us and assure us that we can survive what we are experiencing. When we keep making a mess of our life we need someone to help us face the truths about which we've been lying to ourselves. But when we are given a diagnosis we disappear behind that diagnosis, and the diagnosis is all the unthinking people see.

All of us are already are in the fourth edition of the DSM. According to my copy, on page 673, it states, "301.9 Personality Disorder Not Otherwise Specified". That's you.