Parkinson's disease is a disorder of the nervous system that affects movement, often causing tremors, stiffness and/or slow movement.
Williams died in his California home on Monday from an apparent suicide from asphyxiation by hanging, according to preliminary results from forensic investigators.
The Oscar-winning actor is best known for starring roles in "Good Will Hunting," "Good Morning, Vietnam," "The Fisher King" and "Mrs. Doubtfire."
Read Schneider's full statement below:
Robin spent so much of his life helping others. Whether he was entertaining millions on stage, film or television, our troops on the frontlines, or comforting a sick child - Robin wanted us to laugh and to feel less afraid. Since his passing, all of us who loved Robin have found some solace in the tremendous outpouring of affection and admiration for him from the millions of people whose lives he touched. His greatest legacy, besides his three children, is the joy and happiness he offered to others, particularly to those fighting personal battles. Robin's sobriety was intact and he was brave as he struggled with his own battles of depression, anxiety as well as early stages of Parkinson's Disease, which he was not yet ready to share publicly. It is our hope in the wake of Robin's tragic passing, that others will find the strength to seek the care and support they need to treat whatever battles they are facing so they may feel less afraid.
—By CNBC's Karma Allen