Working on my blog and though this might be an interesting thread. The subject is not simply what has met the standards of research but also those things that are obvious down here on the sea floor. Add and critique if you will.

I. What Do We Know?

1. PD is widely distributed geographically and, with rare exceptions, is not found in a pattern suggesting solely environmental origins. If a factory is belching out a carcinogen, we expect a cluster of cases downwind of the factory. Such horizontal clustering of PD has not been observed in homogeneous populations. While environmental toxins may influence the matter it is unlikely that they have a dominant role.
2. In a similar manner, PD does not exhibit vertical clustering within the levels of a stratified society. The child playing in the gutter seems no more likely to develop PD than the one playing in the penthouse. While social status may influence the matter it is unlikely to be the dominant factor.
3. PD does exhibit clustering among some occupational groups, however. Farmers and welders, for example.
4. PD also is generally more common in industrialized countries than in non-industrialized countries.
5. Family clusters are rare which casts doubt on solely genetic origins.
6. Particular personality traits seem shared more than statistically likely.
7. An exaggerated stress response is so common as to be almost universal in the later stages.
8. The speed of degeneration and the nature of symptoms is highly variable among individuals.
9. A dramatic worsening of symptoms is often associated with infections.
10. A similar response to acute stressors is often incapacitating.
11. Lifetime stress loads are remarkably high among younger PWP.
12. Acute trauma often precedes diagnosis.
13. Acute infection often precedes diagnosis.