In 2004 an online Harris survey brought to light the often disabling non-motor symptons of PD -- well known by patients, but not usually addressed or realized by neurologists. Such as pain, depression, sleep problems, etc.

the survey was in large part completed with the help of PLWP, a grassroots Parkinson's patients group and online discussion groups such as this one (Braintalk in those days)

Description of survey and results :
http://journals.lww.com/neurotodayon...kinson.11.aspx

I can remember when the results were made public, you could hear a collective "DUH!" among PWP worldwide. But non-motor (non-dopaminergic) symptoms are now a focus of research and treatment . Clue: listen to patients.