The cause of Parkinson’s symptoms seems to be varied. As you say, what works for one doesn’t always work for everyone.
There is an American site www.23andme.com Their focus is on DNA of PD suffers and I have given them my DNA. They have all sorts of questionnaires, the only common denominator they have found so far is not based on DNA of the people they have sampled. What they have found so far is that PD people don’t like sky diving and they like sweet things. To my mind sky diving = stress (stress hormone) and sweet things = sugar.
My PD symptoms came after I had a car accident. I wasn’t physically injured but was badly shaken. I had been working 12 hour day and night shifts for 5.5 years prior to the accident. Frankly, I was physically exhausted at that time. I have a sweet tooth as well. So there are the two components “stress” and “sugar”. For me, the other one could be “protein” as it blocks my PD medication.
So the stress hormone, sugar and protein are factors in my case. The answer may be in there somewhere.