The Two Types of Bipolar Disorder
Bipolar I vs Bipolar II
Dividing bipolar into I and II arguably has more to do with diagnostic convenience than true biology. A University of Chicago/Johns Hopkins study, however, makes a strong case for a genetic distinction. That study found a greater sharing of alleles (one of two or more alternate forms of a gene) along the chromosome 18q21in siblings with bipolar II than mere randomness would account for.
A 2003 NMIH study tracking 135 bipolar I and 71 bipolar II patients for up to 20 years found:
- Both BP I and BP II patients had similar demographics and ages of onset at first episode.
- Both had more lifetime co-occurring substance abuse than the general population.
- BP II had “significantly higher lifetime prevalence” of anxiety disorders, especially social and other phobias.
- BP Is had more severe episodes at intake.
- BP IIs had “a substantially more chronic course, with significantly more major and minor depressive episodes and shorter inter-episode well intervals.”
Nevertheless, for many people, bipolar II may be bipolar I waiting to happen.
The DSM’s one-week minimum for mania and four-day minimum for hypomania are regarded by many experts as artificial criteria. The British Association for Psychopharmacology’s 2003 Evidence-based Guidelines for Treating Bipolar Disorder, for instance, notes that when the four-day minimum was reduced to two in a sample population in Zurich, the rate of those with bipolar II jumped from 0.4 percent to 5.3 percent.
A likely candidate for the DSM-V as bipolar III is “cyclothymia,” listed in the current DSM as a separate disorder, characterized by hypomania and mild depression. One third of those with cyclothymia are eventually diagnosed with bipolar, lending credence to the “kindling” theory of bipolar disorder, that if left untreated in its early stages the illness will break out into something far more severe later on.
The medical literature refers to bipolar as a mood disorder and the popular conception is one of mood swings from one extreme to the other. In actuality, this represents only a small part of what is visible to both the medical profession and the public, like the spots on measles. (Many of those who are bipolar, incidentally, can function untreated in the “normal” mood range for sustained periods of time.)
The cause and workings of the disorder are total terra incognita to science, though there are lots of theories. At the Fourth International Conference on Bipolar Disorder in June 2001, Paul Harrison MD, MRC Psych of Oxford reported on the Stanley Foundation’s pooled research of 60 brains and other studies: