Schneider, known for US sketch comedy show Saturday Night Live, took to Twitter to blame the Good Will Hunting star’s cocktail of medication for his untimely death last week.
“Now that we can talk about it, Robin Williams was on a drug treating the symptoms of Parkinson’s,” he wrote. “One of the side effects is suicide!”
Schneider had been friends with Williams since they first met 20 years ago. The latter’s friends were worried that his cocktail of prescription drugs had badly affected his mental health, according to The Mirror.
Parkinson’s is a progressive disease that attacks the nerve cells in the brain, eventually leading to severe movement problems.
Neurological experts believe that Parkinson’s can make depression symptoms worse, although the area is still under study.
Robin Williams: A career in pictures
Robin Williams: A career in pictures
1/30 Robin Williams
1980: Robin Williams in the world-famous Mork and Mindy series that launched his career.
2/30 Robin Williams
1984: Williams in 'Moscow On The Hudson'. The actor earned his first Golden Globe nomination for his turn as a Russian circus performer in this 1984 hit.
3/30 Robin Williams
1987: Williams in the critically acclaimed 'Good Morning, Vietnam'. Williams ad-libbed all the radio broadcast scenes from this 1987 film about a radio DJ sent to Vietnam to entertain the US troops serving out there.
4/30 Robin Williams
1989: Robin Williams appeared with Robert Sean Leonard and Josh Charles in 'Dead Poets Society' as English teacher John Keating - or the “slightly more daring O Captain, My Captain”.
5/30 Robin Williams
1990: Williams and Robert De Niro in Awakenings, an emotional film that saw Williams portray a British neurologist who administered a drug to catatonic patients that briefly awoke them from decades of catatonia.
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1991: Williams appeared as an adult Peter Pan forced to return to Neverland to rescue his children in 'Hook'. The film received mixed reviews but proved popular at the box office.
7/30 Robin Williams
1992: Williams in 'Toys'. The film followed a military general after he inherits a toy factory and decides to produce war toys.
8/30 Robin Williams
1993: Williams appeared in one of his best-loved roles in Mrs Doubtfire, where he played an actor disguising himself as a female housekeeper in order to spend more time with his children.
9/30 Robin Williams
1995: Williams appeared as man released from a board game after being trapped for decades inside it in the blockbuster 'Jumanji'.
10/30 Robin Williams
1996: Williams starred opposite Jennifer Lopez in 'Jack', a film about a young boy who ages four times faster than other children.
11/30 Robin Williams
1997: Williams appeared alongside Matt Damon in 'Good Will Hunting', a film that won him an Oscar for his portrayal of psychologist Sean Maguire. As he accepted his award, a touched Williams warned the audience: "Oh man, this might be the one time I’m speechless".
12/30 Robin Williams
1997: The box-office hit Flubber saw Williams take the role of Professor Philip Brainard, who creates the unstoppable green goo Flubber in his bid to produce a new energy source.
13/30 Robin Williams
1998: Williams gave a poignant turn as Dr Hunter 'Patch' Adams, an unqualified doctor who treats patients with laughter in 'Patch Adams' .
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1998: Williams stars alongside Cuba Gooding, Jr in 'What Dreams May Come', a film that follows American physician Chris Nielsen's journey through the afterlife after he is killed in a car crash.
15/30 Robin Williams
1999: Robin Williams, Bob Balaban (left), and Armin Mueller-Stahl star in the movie 'Jakob the Liar' about a Jewish shopkeeper who uses his imagination to engender hope throughout a Polish ghetto in 1944.
16/30 Robin Williams
1999: American Science Fiction drama 'Bicentennial Man' followed an android (Williams) as he experiences emotions and becomes more human
17/30 Robin Williams
2002: Williams took a more sinister role as reclusive crime writer and murderer Walter Finch in 'Insomnia'.
18/30 Robin Williams
2002: Williams undertook an unsettling, psychopathic role in One Hour Photo, where he played a photo lab technician obsessed with a family who frequented the store.
19/30 Robin Williams
2002: Williams starred alongside Danny DeVito in 'Death to Smoochy', a film about a corrupt children's television host disgraced by an FBI sting.
20/30 Robin Williams
2005: Robin Williams stars in 'The Big White', a film about a financially struggling travel agent trying to make a bogus life insurance claim in order to pay for his wife's Tourette treatment.
21/30 Robin Williams
2006: Williams and Ben Stiller star in 'Night at the Museum'. Williams will appear in upcoming film "Night at the Museum: Secret of the Tomb," playing the statue of Teddy Roosevelt who comes to life at night.
22/30 Robin Williams
2006: Robin Williams, Jeff Daniels and Cheryl Hines star in roadtrip comedy 'R.V.', which followed the tribulations of a dysfunctional family.
23/30 Robin Williams
2006: Williams took the leading role in the political comedy drama 'Man of the Year' about a comedian who decides to run for President and finds himself mistakenly elected.
24/30 Robin Williams
2007: Robin Williams and Freddie Highmore in 'August Rush', where Williams played a homeless musician who teaches children living on the streets music and employs them as performers.
25/30 Robin Williams
2007: Robin Williams, Mandy Moore and John Krasinski starred in 'License to Wed'. Williams played a reverend who places a couple through a series of tests to see if they should marry in his church. The rom-com was poorly received by critics.
26/30 Robin Williams
2010: Robin Williams and John Travolta star in 'Old Dogs', a comedy that sees two friends and owners of a sports marketing firm struggle to deal with seven-year-old twins placed in their care. The film was nominated for four Golden Raspberry Awards.
27/30 Robin Williams
2013: Susan Sarandon, Robert De Niro and Robin Williams star in The Big Wedding
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2013: Williams starred as President Eisenhower in Lee Daniels' 'The Butler'.
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2014: Robin Williams with his Mork and Mindy co-star Pam Dawber in The Crazy Ones series. It was axed after one season.
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2014: Rob Williams stars in 'The Angriest Man in Brooklyn', the story of a bad-tempered man mistakenly told he has 90 minutes to live.
Actor Michael J Fox, who discovered he had the illness in 1991, revealed his shock at Williams’ diagnosis on Friday.
The Back to the Future star said he was “stunned” at the news as he had no idea that his “true friend” had been keeping his suffering hidden.
Video: Stars and fans remember Robin Williams
Williams was "not yet ready to share publicly" his struggle with Parkinson's, his wife said in a statement.