Electric car maker Tesla’s CEO Elon Musk has admitted in a newspaper interview that stress is taking a heavy toll on him personally in what he calls an “excruciating” year.

The New York Times said Mr Musk alternated between laughter and tears during the interview in which he said he was working up to 120 hours a week and sometimes takes Ambien to get to sleep.

“This past year has been the most difficult and painful year of my career,” he said. “It was excruciating.”

The interview offered rare insights into Mr Musk’s personal life and thinking.

He stood by his tweet last week saying he might take Tesla private and that he had secured the funding to do so.

Asked if he regretted it, he said, “Why would I?”

Mr Musk has a reputation for being an eccentric visionary. But his out-of-the-blue announcement of a potential $72 billion (£57 billion) buyout of the publicly held company raised a huge ruckus and pushed Tesla’s shares up 11% in a day, raising the company’s value by $6 billion (£4.7 billion).

They have fallen back but remain elevated.

The Wall Street Journal reported that government regulators have subpoenaed Mr Musk as they dig deeper into his disclosure of the potential buyout.

That signals regulators are investigating if Mr Musk was truthful in the tweet about having the financing set for a deal.

The company did not comment on that report, but it did say it was forming a special committee to evaluate proposals to take the company private.

The newspaper said that in response to questions for its article on the interview, Tesla issued a statement from its board, excluding Mr Musk, that said: “We would like to make it clear that Elon’s commitment and dedication to Tesla is obvious.”

In the interview with The New York Times, Mr Musk said he fired off the tweet while on his way to the airport.

He said his reference to having secured funding referred to a potential investment by Saudi Arabia’s government investment fund.

The 47-year-old said sometimes he did not leave the Tesla factory for three or four days straight, and that he had not taken off more than a week at a time since he was sick with malaria in 2001.