The news today is -- at least on the surface -- about changes that have been proposed in the medical definition of autism. Here is a link to a representative news story:

http://www.nytimes.com/2009/11/03/health/03asperger.html

The key change is from a categorical system (you either have it or you don't) to a continuous system in which every person would have a numerical rating which describes how autistic they are, just as everyone now has a weight, height, BMI, IQ, etc. In the new system, in other words, some of us will be seen to be more autistic than others, on a spectrum.

This is likely to be merely the first in a series of similar changes in way in which the medical profession defines mental illness. Next up will be the depression and anxiety disorders. Instead of dividing the world into people who have a depressive illness and those who do not, for example, we will each be seen as having a quantitative propensity for depression. Medical treatment will likely be indicated by a threshold, just as it is now for many organic conditions (your SGOT score, for example).

I expect the same thing may happen to narcissism. At the moment we have a "narcissistic personality disorder" which one either has or does not have. In the future, everyone will instead have a score on the narcissism scale.

Many diagnoses will not make this change: organic brain disease, for example, and schizophrenia. The current diagnosis of bipolar disorder is likely to split into at least six different disorders; some may be binary (you either have it or you don't) and some quantitative.

Personally, I think these changes are overdue. Many psychiatrists and clinical psychologists already think this way, but now the official diagnostic criteria are catching up. Psychiatry is a medical profession, and they have retained the old medical disease model out of loyalty to tradition, but it many cases it just hasn't been able to withstand detailed scrutiny. We just aren't either autistic or not autistic -- the evidence for the existence of a spectrum is simply overwhelming. We are all a little autistic, a little depressed, a little anxious, a little narcissistic, but some may peg the meter. Those are the ones in need of medical treatment or psychotherapy or some kind of intervention.

Even in the case of purely genetic diseases, the expression of a troublesome gene is often modulated by non-gene sections of DNA, which means that we have to talk about phenotypic variation -- a quantitative concept. Very few genes are expressed in a binary fashion, countless statements in the popular press to the contrary notwithstanding.

After these conceptual changes have run their course (a process that may take a good twenty years), the relationship between psychiatry and psychology will be fundamentally different. It's going to be interesting.

Loren