For years, staff and investors have tried to brush off Musk's odd behaviour by blaming it on his creativity, mental health, and lack of sleep. But according to the Wall Street Journal his drug use is starting to worry them more.

The Journal says that Linda Johnson Rice, a former director at Tesla quit the electric car firm's board over Musk's drug use and mad behaviour.

Rice, who was on Tesla's board for two years until 2019, reportedly told other board members more than once about her fears over Musk's drug use.

The report said that Rice even suggested that the board should look into Musk's drug use, which includes stuff like ketamine, LSD, cocaine, and ecstasy. Her fears were ignored so she left.

The Journal showed how bosses in Musk's various firms have struggled with his drug use and crazy public acts and words.

At Tesla, some current directors have asked for help from Musk's brother, Kimbal Musk, about Elon Musk's behaviour, but they have been careful not to say "drugs" in chats about their worries.

The Journal also pointed out guesses from some people who thought that Elon Musk may have been high when he tweeted in 2018 that he had "funding secured" to take Tesla private at $420 a share.

This tweet hit Tesla's stock price, leading to an SEC probe and $40 million in fines for Elon Musk, although he did not say sorry.

The billionaire businessman has said various things about his drug use, including saying that he sometimes takes small doses of ketamine.

He has also been seen using the drug for fun and publicly said that, in his view, ketamine "is a better option" than treating depression with SSRIs.

Musk famously smoked weed with Joe Rogan on a podcast, which made NASA do a safety check of SpaceX and make the whole firm do drug tests for a year.

The Wall Street Journal quoted a lawyer for Elon Musk, Alex Spiro, who said that the SpaceX and Tesla boss is “regularly and randomly drug tested at SpaceX and has never failed a test.”

Spiro added in reply to the paper's detailed questions that “there are other false facts” in The Wall Street Journal's article but didn’t say what.