In order to draw fire away from Steffi's direction, here are some factors that explain a lot of this. Some of this is part speculation but far less than what most neuros have been taught. This is the emerging view of PD as well as several related disorders and most of it is backed up by some serious research. If you wish to go deeper, explore the work of P.M. Carvey at Luke's in Chicago, Bin Liu at the NIH in North Carolina, and Bruce McEwewn at Rockefeller University University in New York.

PD is not a neurological disease. Try to sell that to your neuro. PD is actually a disorder of the endocrine and immune systems that cause damage to the nervous system. The neurological stuff is symptom, not cause. Most current treatments are symptomatic and leave causes untouched.

Two basic forces at the core with one or more secondary ones around the perimeter. At the center are immune response to the bacterial toxin lipopolysaccharide (LPS) and endocrine response to stress. Both start in the womb and interact throughout our lives.

This intertwined pair both originate and work as a unit. If a fetus is exposed to LPS during a critical moment in development it has fewer neurons in the SN, its stress response is screwed up, and it is hypersensitive to future exposure. One source of LPS is maternal infections. Another is house dust. Either of these can easily look like a genetic family cluster.

If a fetus is exposed to maternal stress hormones during a critical moment the effects are similar. Damage to the nervous system. Screwed up stress response. Hypersensitivity to stress hormones. One result is that a stressed-out mama can produce a stressed-out baby. But what is really interesting is that she can also produce a stressed-out grandbaby! If the stress comes from the family structure (daddy a drunk?) then again the semblence of a genetic link.

At the same time there is an effect on the GI system both structurally and in the colonization of the bowel. Earlier conversations on this forum showed about half of us remember constipation as a childhood problem. Constipation allows time for toxins to reenter the system.

This is the core but is not enough alone to trigger PD. But start adding in those secondary factors... genetics, personality, pesticides, metals, gender, etc. The more of this the greater the chances of PD.

With the right mix we grow up to be people who deal with anxiety by taking charge so that the job is done right. We thus tend tto be overachievers.

We tend toward "cool, calm, and collected" but chronic elevated levels of cortisol eat at us over the years and eventually a ringing telephone can incapacitate us. Added to this endocrine problem is the immune counterpart - a constant systemic inflammation that eventually triggers our microglia to destroy our substantia nigra.

The odd thing is that all the explanations fit. Yes, the SN is damaged. Yes, dopamine makes us feel better. Yes, some families have more than their share of cases. Yes, NSAIDs lower the risk. Yes, stress sensitivity is one of our biggest problems. And on and on.

This is overly simplified, of course. It has to be. We have a very interesting disease, my friends.