Hi Rick,
I agree with Carolyn that everyone in modern living is stressed, but there is stress and extreme stress. I was born in 1936, and my parents had just bought their first house, with a heavy mortgage. My father was frequently out of work, and income was spasmodic. I remember my mother telling me that at one time, my father had raging toothache, but had not the money to go to a dentist. His schooling had stopped at 14, and he had given a false age when he was 16, to get into the army and fight in WW1. The storm clouds of WW2 were gathering, and it was clear there was going to be a war. My brother (aged 4 when my mother was carrying me) had a dreadful skin disease, and had to be bathed and covered in fresh bandages every couple of hours.
Times were much harder then, and I feel my mother was under extreme stress at the time she carried me. One thing that argues against this theory in my case, is that my sister was born in Feb.1942, and 9 months earlier, the German blitz fell on where we lived in Liverpool. I remember the bombing vividly, the German bombers were aiming for the vital docks, but with no laser targetting, they tended to saturate whole areas with bombs, (shock and awe!!!) Houses all around us were destroyed, and we waited for it to be us.
So why doesn't my sister suffer from PD? The only thing you can say about that is, she is in her mid 60's, and doesn't suffer YET!! I am 70.
I have raised previously the effect of a stress situation (which is known to open the pores of the blood brain barrier, (BBB) and admit toxins to the brain). I believe this is the cause of the worsening in symptoms in PD in a stress situation. PD people have been shown to have a more porous BBB or "leaky" BBB.

See
http://neurotalk.psychcentral.com/showthread.php?t=190
&highlight=Blood+Brain+Barrier


Presumably, the foetus similarly is given a dose of toxins when the mother suffers extreme stress, so maybe there is something in this idea. There may be a reduction in dopamine neurons, but enough neurons to last a number of decades, before natural loss of neurons with ageing, causes the threshold of 20% left, and PD symptoms start to show.

Ron