Moving from "your diagnosis"
"your position on a spectrum"
The "rule book" for diagnoses in psychiatryDSM was developed primarily to help straighten out research. We needed clearly separate "diseases" to standardize research results. For example, you could ask how many people with "major depression" will respond to Drug A, or Therapy B. When that is known, then someone who has the same symptoms might be told she/he has that likelihood of responding to Drug A. The problem is, no two people have exactly the same pattern. And the patterns start to blend in with one another at their edges.
This led to the growing recognition that symptoms can occur along "spectra". Here are some "spectrum" examples (based on a presentation by Dr. Ketter, head of the Stanford Bipolar Clinic):
(Schizotypal PD)...Schizophrenia..........Schizoaffective Disorder....... Bipolar I
Sad..........Unipolar Depression.............Bipolar II............Bipolar I
Temperament............Bipolar II.............Borderline Personality Disorder
As an analogy, imagine that people are like cans of paint. Everybody starts out basically neutral, then genes and experiences add colors to their can. If you end up with too much of one color, you'll "stick out" compared to everybody else. We might call your difference a "symptom", if it causes you to have trouble with functioning in society.
Applying this analogy to the "spectrum" way of diagnosis, a person who has just a little anxiety pigment might be shy; but a person who has a lot is so afraid of groups that he merits a diagnosis of "social phobia". And if he gets a maximal amount of that pigment, he's so afraid to go out in public that he avoids doing so almost entirely: "avoidant personality disorder". A person could get any amount of this "pigment", but we only have three diagnostic terms for that continuous spectrum of differences between people:
Shyness...........................Social Phobia.............................Avoidant Personality Disorder
Borderline or bipolar? A "pigment" answer
Now let's take the "paint" approach to "borderline vs. bipolar", a common diagnostic disagreement. You may have already seen my essay on this, which notes the almost complete overlap of symptoms between the two diagnoses. With that much overlap, these people must have basically the same "pigments". One person might have gotten them from genes, the other from experience -- we can't tell the difference yet.
However, one pigment seems to differ in each.
They both have red for hot emotions, and blue for depressive symptoms, and a sparkly pigment that makes them impulsive. But the "bipolar" person has a magic ingredient that makes her pigments vary cyclically over time. There is some consistency to the way this magic pigment works: she tends to be either one way, or another, all symptoms varying together. Remember, this magic stuff is another "pigment". She could get a big dose of it, and be bipolar I: extreme swings separated by years, looking much the same each time they reappear. If she got a small dose of the "vary" pigment instead, her symptoms might be less clearly "cyclic", more mixed and muddled.
On the other hand, the "borderline" person has a green ingredient that makes her feel empty, and feel much worse in this way when she is alone. Plenty of people who wouldn't be called "borderline" have quite a bit of green in them, but if you get a lot of this green pigment, you're more likely to have trouble in relationships. When two very green people get together, each will feel badly when the other goes away somehow (including emotionally; for example, if one gets mad at the other). Imagine what happens in a relationship if one person is very green, and the other is not; this can be as troublesome as when both are green. You've heard these matches described as problems of "co-dependency". How much "green" a person has seems to depend on both genetics and experience: some kids just turn green no matter how good an upbringing they get; others can develop emptiness from experiences that they had growing up (lots of real or perceived abandonment may do it; certainly sexual abuse seems to do it).
Just to make it clear that this is not "always somebody's fault": the "match" between a child's temperament and the parenting they receive can be the problem, not the child's temperament or the parenting either. Some kids can handle a pretty distant parent okay; others can be devastated by this. Some kids will feel "smothered" by an involved parent; others will thrive with such attention. Children can show these differences right from birth. You can read more about this "match" in the superb scholarship of Marsha Linehan, Ph.D. Warning: her book "Cognitive Behavioral Therapy of Borderline Personality Disorder"Linehan prompted a psychiatrist friend to say: "never have I read so important a book that was so boring". Dr. Linehan repeats the same themes over and over, but for good reason: they're crucial themes to understanding this personality. You could go to a bookstore that has it and just read the section on "Emotionally Invalidating Environments": it's in the first chapters just after the definition of the disorder.
So, to summarize: diagnoses are not based on known chemical differences. They are conveniences for researchers, and are also supposed to help you find the right treatment. But because symptoms are spread over spectra, from a little to a lot, labels can often be misleading. Finally, borderline patients have most of the features of bipolar, plus an emptiness streak; and may have less clear "cycling" of their symptoms.
Visits since counter set October 15th, 2005: