Williams' widow, Susan Schneider, released a statement Thursday, saying the actor wasn't yet ready to go public with his Parkinson's diagnosis at the time of his death.
Schneider emphasized that Williams was sober at the time of his death.
Schneider says she hopes this additional information about Williams will encourage others "to seek care and support to treat whatever battles they are facing so they feel less afraid."
Robin Williams was 63 years old.
Copyright 2016 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.