There are going to be some changes made, according to news stories on the reports of the groups working on the next edition of the Diagnostic and Statistical Manual of the American Psychiatric Association. One change that's been attracting a lot of attention is the move toward eliminating Asperger's syndrome as a diagnosis and combining Asperger's symptoms with those of another mild form of autism to create a new category. The new edition, DSM-V, will probably do this.
Asperger's syndrome was first listed in DSM in the 1994 edition. It was described as a mild form of autism involving social and physical awkwardness, sometimes but not always combined with verbal precocity and intense but limited learning interests. (This description reminds me of one of my office-mates in graduate school, who could and would recite or write out lists of the names of organ stops like "vox humana"-- which did not make him the life of any party.) But now it seems that Asperger's syndrome is going away.
What does this change mean? Don't people have the symptoms of Asperger's syndrome any more? Of course that's not the case. But let's look at mental health problems as they are reflected in years of DSM editions. Most of the problems whose symptoms are listed have no well-understood physical or genetic causes that would help to define and diagnose them. Few of them have well-understood causes in childhood or adult experiences. And in a lot of cases there is considerable overlap between the symptoms of one diagnostic category and those of others. In addition, both the names and the symptoms of some diagnoses have changed over the years. For instance, Reactive Attachment Disorder, a category now considered to involve disturbed behavior of children toward adults (both unusual willingness to approach strangers and unusual aloofness toward familiar people), was initially defined as part of an eating disorder of infants and young children.
Although a small number of mental illnesses have specific causes or characteristics, there is a broad spectrum of mental illness, with individual differences among diagnosed persons as great as individual differences in personality among the mentally healthy population. Just as children with handicapping conditions continue to grow and develop along their own trajectories, both children and adults with symptoms of mental illness display their own personality and developmental stage characteristics. A recent article in the New York Times "Science Times" section (Wallis, C.[2009, Nov.3]. "A powerful identity, a vanishing diagnosis". D1, D4) noted that autistic disorders in particular may change over time, with children changing symptoms sufficiently to receive different diagnoses at different ages.
Mental illness is not like chickenpox or measles, where the causes are the same for everyone and most of the symptoms will be the same for every infected individual. In physical illnesses, Nature itself provides built-in categories that do most of the work of determining the diagnosis. To a considerable extent, though, the variations of mental illness make categorization the job of the researcher and practitioner, who try to establish guidelines that discriminate between various kinds of emotional disturbance. This is an ongoing job that is affected by new research and by changes in cultural and professional values. A famous example of the influence of cultural changes is the removal some years ago of homosexuality from the list of diagnoses in DSM-- a change brought about by alterations in cultural attitudes toward variations in sexual orientation. It's less well-known that the present work on the new DSM is influenced by the concept of evidence-based practice, a relatively new value in the professional subculture; diagnoses to be included in DSM-V are expected to be supported by empirical research evidence.
What is the point of having DSM at all, if the categories of mental illness are so difficult to describe? To a considerable extent, the point is to simplify communication. For example, rather than having to write or read a lengthy narrative description of a patient, a practitioner can use a diagnostic category to give a general understanding of the problems that are giving concern. For research purposes, it's necessary to define the characteristics of the population being studied, and DSM diagnoses are helpful in this. Although there are few mental illnesses that have treatments specific to the diagnosis, where such treatments are proposed, evidence for their effectiveness can be established only if there is agreement on the diagnosis. Finally, there is the well-established use of DSM categories for purposes of establishing insurance coverage and payment (and a few decades ago, the diagnosis of autism was not covered in this way).
Wallis's article in the "Science Times" referred to an issue about the Asperger's category that is completely apart from the reasons just mentioned for having DSM categories-- completely different, but potentially very powerful. This is the existence of an Asperger community that may or may not consider the diagnosis an important part of their identity. That community and the rest of the public will be invited to comment on the Asperger's working group's report on the DSM web site, http://www.psych.org/MainMenu/Research/DSMIV/DSMV.aspx, in January.